The most obvious reason is to save space in your home. Space that could be put to much better use. It also allows you to angle your TV in any direction you choose, giving you a perfect view from any seat in the room.
But there are even more important reasons why wall mounting your TV is a good idea:
You may not often think about it, but accidents often happen at home. If your TV is on a floor stand, it can always fall off. Avoid this happening by mounting your TV on the wall!
No matter from which direction the sun is shining, with a full motion TV wall bracket, you'll never be bothered by glare again: by turning your TV slightly, using the wall bracket, you can avoid annoying glares and reflections.
You only realise how much space a TV takes up once you've mounted it on a wall bracket. In short, mounting your TV gives you so much extra space (especially if you toss out your old TV furniture...).