Parallax is all about look, so yes, it is useless. You like it, then good. Is it nice? Yes, but it has no functional purpose. That doesn't mean Apple hasn't come up with a some new ideas for it that remain to be seen.
Neither does the transparency/ 'frosted glass'. Is it nice? Yes, but it has no functional purpose.
You sound like the OCD type where everything has to have a purpose and function...what if it's function is to look nice? I take it the walls in your home are bare then?