But imagine if your next desktop build required you to also throw away your SSD, monitor, keyboard, mouse, and speakers. You can also re-use a case in future builds, and re-use a high quality PSU in future builds.
I also don't really care to replace individual components in my systems, but being able to upgrade laptop hardware without throwing away the chasis and storage seems pretty nice to me.
My next desktop build will require entirely new parts, and the prior build will be demoted to other uses, or given to someone else who has a better use for it. As a whole unit, it still has utility. If I scavenge an essential piece, all the rest go to waste.
If it were a big energy hog (it's not), then it may make sense to put it out to pasture and scavenge the parts for others.
The exception is my keyboard, is like my toothbrush, if toothbrushes could last for two decades. That I will keep and move to the new computer, as keyboard technology is not advancing.
For laptops, I see even less utility for upgrades than for a desktop, but perhaps that's just me.
Easy upgrades mean easy repair. The opposite is also true.
You can move your keyboard to a new computer because you are able to detach it without melting half the device with a heat gun. With laptops it's not that easy. When the MacBook keyboards broke all the time a few years ago, a keyboard replacement meant also replacing the speakers, battery and touchpad. Not for any technical reason, but because Apple doesn't like screws. The MS Surface Pro and Surface Laptop couldn't be repaired by anyone, not even MS themselves - if a single $20-30 part fails you have to spend $1000 again. Doesn't sound like a great deal if you ask me.
You might not need or want upgrades and maybe you're lucky and nothing ever breaks. But having the choice only comes with upsides.
I also don't really care to replace individual components in my systems, but being able to upgrade laptop hardware without throwing away the chasis and storage seems pretty nice to me.