A bit like cars. They have more 'stuff' to run, elec windows elec everything, pc's, etc etc....etc......so they need more 'battery'...and much smarter use of that 'power'
To me Ubuntu is a totally bloated mess, dragged down by snaps, yeah, I am biased. obviously.
I use Linux Mint with 32GB of ram. It flies. The PC?.....made prior to 2014....only reason I know is that is when I picked its sorry carcass up from a local tip. Out in the weather, half full of insects, mud, etc. bits hanging off it everywhere.
It now runs an nvme, an ssd. and a 2TB external, plus the mandatory headphones, Logitech Cinema speakers, an extension piece that has 6 usb ports.... (I dislike having to reach around the back of it to get to usb ports,,,,ones on the front have stuff in them) ...recently I had to replace the Power supply....the rotten thing had the temerity to die,
I just felt like saying all that.
Ubuntu....not for me. i have tried to like it. Many times. It reminds me of pushing a pram full of bricks instead of a baby.
Obviously I am aware that Mint is based on Ubuntu. The differences that Clem & Co pump in to each and every iteration of Linux Mint is nothing short of amazing. Likewise their latest and greatest LMDE.
The amount of crap and junk which they brush aside/keep out is heart warming.
So, after all that waffle, am I surprised that Ubuntu needs more ram to 'function' ?
No.
Hope you enjoyed/sufferred gladly, the waffle.