I’d say it’d be quite a bit still in 2 years. My 5s I traded in a month or two ago was still worth $100+ if you sold it. And that was a 5 year old phone.

7’s are still worth over $300.

Laptops and desktops typically last a lot longer though. My current laptop (Surface Pro 4) is >2 years old, daily use and a fair bit of travel, and still as good as new, expecting at least a couple more years out of it and even then I'll likely replace more because I want a shiny new toy than because it's no longer good enough. I still have an 8 year old Lenovo laptop which works fine (switched the hard drive for an SSD and added more RAM a couple of years ago).

Phone batteries start to get pretty poor after a couple of years, Apple as we now have confirmed also slow the older phones down. And it sometimes seems as if half the people I know have cracked phone screens. I know there are people who make their phones last forever, but I think most smartphones that are used heavily every day are pretty much done after 2-3 years, which is less than half the lifetime of a decent laptop. Desktops have even more longevity since you can basically open them up and keep on upgrading if you've got a decent case.

Batteries die on laptops just as fast you just generally don’t notice as they are plugged in more regularly than phones.

The reason you phones don’t seem to last as long as computers is because of how quick online/apps etc are improving. Computers have been able to run most things being streamed online, most games and programs for awhile, minus some heavy duty stuff. Phones still aren’t at that stage. When phones get to the point where improvements in the software and how much power they’re using level off phones will start lasting longer too.

Not noticing the battery decline in my laptop is basically because I don't need it as much as on a phone, so it's less of an issue. I normally end up replacing my phone around the time that I find myself carrying a recharging pack every time I'm on the move for more than a few hours. Laptops I either replace the battery if it's bothering me (not easy on the Surface admittedly) or more commonly after ~5 years it's starting to seem clunky compared to newer machines and I get tempted into a shiny new model that I don't really need.

I do think the physical wear and tear on a phone is a contributor to their lifespan, they tend to take a lot more abuse than a laptop.