Space and time are related. We call them together 'spacetime'.

You have a limited and fixed speed through spacetime.

If you are statioanry, then all your speed goes into time. You get to go the maximum rate through time. We'll call it aging 1 second per second.

If you move, then you have to split your speed between time and space. If you move slowly through space, then you might age 0.999999 seconds per second, which is hardly a ntoicible difference. If you move very fast through space, then you might age 0.10 seconds per second, which is a very noticible.

Some objects move just fast enough, and need precision timing enough, that we notice it. Like software that works with GPS satellites needs to account for the tiny time dilation between them, because that tiny difference would make a difference in where the GPS believes you are.