Imagine you want to gain access ti your coins in 20 years and the hardware wallet is broken. Yes you can buy a different new one but you could also fix the broken part of the old one.
I don't think many people would know what is wrong with their device if they connect it and it's just dead. It's not like the hardware wallet will tell you:
Hi, change my display to continue or
my chip is fried, please buy a new one. The wallets would require a complete hardware changeover just to satisfy the needs of a minority of people who would be interested in experimenting with fixing the problems themselves. I don't see that happening.