You didn't mate.

>Why is this a thing now?

You seemingly not understanding why this is a thing.

> Artificial trees used to always come in 2 parts. You had to assemble the top to the bottom.

You commenting on top and bottom parts, different from a left and right part / only half a tree which can be put flat against a wall.

>Which was easier to decorate everything but the lights on the top portion.

More about the top.