There are three major causes:

1. Erosion. Wind, rain, snow, ect. gradually wear down craters on Earth's surface over time.

2. Fewer surface impacts per m^2 . Because the Earth has a relatively thick atmosphere, a lot of the smaller rocks break up before hitting the surface or slow sufficiently to mitigate their impact on the surface.

3. Tectonic activity. Unlike the Moon, the Earth is still tectonically active, with volcanos faults gradually erasing some craters.

Well for one thing the earth does have craters, but they’re often underwater, but the earth also has a thick atmosphere (compared to the moon’s) which breaks up most of the asteroids before they can do much damage to the surface of earth.

Earth is geologically active. The moon is not. Volcanoes cover and "heal" those craters. We DO have them but they're far less pronounced.

I think little space debris that slams into the moon at astronomical speeds does not make it through to us because of our atmosphere. We do have huge craters on earth, so inevitably we will have another. I wonder when.

Earth has a much more active surface than the moon. Plate tectonics constantly recycles crust by burying it and making new crust, weather erodes crust, etc. Granted, this is a slow process, but it took the moon billions of years to look how it does today, because those processes don't operate there. So there is virtually nothing to erase those craters.

In short: Atmosphere.

A lot of meteors that come in contact with earth burn up in the atmosphere, and don't make an impact.

Furthermore, there are a lot of impact craters that have been worn down by weather, covered over by plant growth, and so forth - again, essentially due to the fact that we have an atmosphere.

The earth has an atmosphere. When the earth passes through a cluster of asteroids (this is what causes meteor showers) the vast majority of them burn up in the atmosphere due to air resistance before they can reach the ground to make a crater. The moon technically also has an atmosphere but it is so thin that we don't really consider it an atmosphere. It can't be breathed and it won't slow down, heat up, and burn away objects that pass through it like earth's atmosphere. This means that when the earth and moon pass through an asteroid field the earth is protected while the moon just gets slammed over and over again.

On top of that, the earth has geological activity such as erosion which can erase the signs of old meteor impacts. The moon doesn't have this so every time a meteor strikes, the crater remains there until another meteor hits and obscures or covers it up with another crater.

1. The moon itself. It's a pretty big thing in its own right with its own gravitational field, and it's orbiting around Earth. A lot of things that would hit our planet end up hitting our moon instead because it's out there playing defense.
2. The atmosphere. If it's not big enough, it just burns up, and even if it is big, it's both smaller and slower by the time it makes it to the surface, both resulting in smaller craters. When the moon gets hit, it's full-size and full-speed.
3. Weather and plate tectonics. The surface of Earth is changing all the time and even a huge crater will eventually disappear. Craters on the moon more or less just stay that way until another crater lands in the same area and makes a new overlapping crater.

The vast majority of space rocks crashing down towards Earth is vaporised into dust by the immense temperatures generated by the friction with the atmosphere. Pieces rarely reach the Earth's surface and they're usually tiny if they do. That being said bigger meteorites do impact the Earth, like the one in Russia a few years ago, usually though they fall into the ocean.

There are craters on the Earth too, it's just that most of them are not easily visible since they're usually overgrown with trees and plants. By contrast the moon has no atmosphere or an active eco system so not only does it get a lot more impacts but all the craters are very easy to see.

Lots of reasons, but primarily because of our atmosphere. Lots of things try to hit Earth, but get burnt up on the way down. That, and our landscape has so many other factors acting on it (weather, tectonic plates, things living on it) that what craters do form can quickly be worn away.

The Moon has no air. So that means if an asteroid hits it, it leaves a crater. Then there's nothing to get rid of that crater. It just stays and stays forever.

The Earth has air. And volcanoes. And plants. And water. So if an asteroid landed in the middle of Ohio ten thousand years ago, that's ten thousand years of rain and wind and stuff to get rid of the crater. It might still be there, but it'll look a lot more like a natural valley now. Floods and rivers and tornadoes will knock down some of the hard ridges, and trees and plants and things will gradually soften the landscape as well.

Plus the atmosphere acts like a shield, burning up most asteroids before they cause big impacts. So something that causes a big crater on the Moon will cause a really small crater on Earth, and something that causes a small crater on the Moon will never even hit ground on Earth.

A lot of people are mentioning the Earth's atmosphere here, and it just isn't that big of a factor for sizable impactors over history. Yes, it keeps dust-sized particles from making a constant stream of micro-craters, and stops the fist-sized rocks from making small craters, but even Venus with 90 times Earth's atmosphere doesn't stop any craters bigger than about 2 km from being formed.

Okay, we wouldn't be seeing many craters bigger than the atmospheric cutoff being formed today because the influx of such objects is currently very small, but if we could have had the protection of our atmosphere while somehow turning off erosion/volcanism/tectonism for the past 4.5 billion years, then we would look (from a distance) as cratered as the Moon does--only when looking at small scales would we notice the difference.

Earth has an atmosphere where lots of that stuff burns up.

The moon doesn't.

Also there is erosion and weathering happening on the Earth. That's not happening on the moon.

Earth is full of craters. Some may argue half of it is a huge crater : https://www.esa.int/ESA_Multimedia/Images/2010/04/Earth_Explorers_The_Earth_s_true_shape