Linux uses half the RAM Windows does in a fresh install. 8GB can absolutely be done on a Linux system without worry. To aid systems with 4-8GB RAM, Windows compresses. This has allowed OEMs to ship systems with 8GB as a minimum. This just isn’t enough for multitasking. The CPU is tasked with constantly compressing and decomposing if you’re attempting to multitask. This can make an already cheap laptop feel a little more sluggish. 16GB has always been the minimum for gaming systems and these days it’s becoming apparent 32GB is needed. 8GB is just pitiful for a computer these days.

Addressing the OP, mobile devices used to only need 2-4GB for the longest time. The OS wasn’t that heavy because the ARM CPU could only do so much. As the CPUs improved, higher resolutions were used, prettier animations and more features got added. This all needs more RAM. Android developer options will tell you how much RAM you’re using. A feature of Android is to keep a process cached in RAM that’s been recently used. This is present to aid in battery life. Even if you swipe the app away from recents list, a portion is cached so the next time you start it, the CPU doesn’t have to work as hard to load it up. You can see this under Running services > Cached processes. This means it’s more beneficial for the mobile device to have more RAM.