Why do people like this so much? It seems every web site does it these days and I HATE it personally. It takes up precious screen space for something that isn’

Why do people like this so much? It seems every web site does it these days and I HATE it personally. It takes up precious screen space for something that isn’t useful enough to need to be on screen constantly. And I can always just tap the top of the screen to jump to the top in a fraction of a second.