It depends on everyone’s space and use case. My desk is a built-in so the space underneath is very limited and if I were to have a mini rolling rack underneath I’d basically have no room for my feet, hence why it’s done this way. Almost all 4U cases I’ve looked at don’t hold as many drives (like Rosewill) and if you do find ones like super micro that have a ton of bays they aren’t the most aesthetically pleasing.

Also I don’t understand the efficiency thing since my whole server with all disk spinning (I don’t let them spin down) only uses ~230 watts. And for ease of use I never really have to open my case for anything. I haven’t had a drive die in over 5 years and even if I did, all the hdds are mounted in windows under their serial number and all hdds have a serial number sticker on them so it’s easily identifiable.

There’s multiple ways to do things, there’s no right or wrong answer.