I have spent months at a time getting 7-8 (amid years of 5-6). I never notice any difference and am actually surprised my body can do 7-8 to no purpose.

From the perspective of evolution there's a purpose... burn fewer calories in the dark when there's nothing else to do.

The question is whether it still matters in the modern era.

I think this is pretty common! More sleep makes everything better -- attention, immune system (getting colds less often), mood, etc.

I feel like a different person sometimes. And going to bed even 1hr earlier makes it generally much higher quality.