In theory you could treat desktops the same way. Any hardware problem? Discard entire machine.
This is obviously wasteful compared to replacing only the component which is broken. But it's hard sell to label that as a disadvantage.
I'd wager that sending a laptop back and forth twice is probably about as expensive as a single round trip for a desktop, and with less risk of breakage, since all the parts are soldered in place, with much less wiggle room for heavier stuff to break off.
This is what I do with my laptop today. I am considering building a SFF desktop in the future just to have, but before I do so I'd like to find a robust and performant solution for TB4 switching, at which point I'd use the same set of peripherals and input devices for both systems.
Going down to mini-ITX motherboard size means I'm going to probably be low on ports and expansion options, so having a dock will be an important part of the setup, and will also help reduce cable clutter/cable shuffling.
One other thing I might look into is an audio switcher. I don't have an 'audio stack', but usually can't stand the electric whine on most basic onboard audio. If I can keep my headphones on, and just flip a switch to change the channel they receive from, I'd be thrilled.
Support and warranty work is simplified when you only have 4 or 5 models of computer in your org, and can reference a spreadsheet to see exactly what a given user has in front of them.
I still prefer a desktop PC for my personal use, because I play videogames, and a desktop is what's historically best for that. A side benefit of having a personal desktop means that I can reuse whatever peripherals, furniture, etc between either my 'work' or 'home' desk configuration.
If I wanted to go full-circle optimized for my next PC build, which I may as well think about, I could plug all of my peripherals into the same thunderbolt dock, and only worry about that one cable, instead of the (potentially) 4 USB devices I'd be switching back and forth.