What OS are you primarily using? I’d imagine Kali for pentesting if you do that, but what do you use everyday?
Because they’d rather sell you a new phone than have you repair your device so it lasts longer. It’s capitalism at work. Same reason why everyone and their mom is moving their products to a subscription model. They want that steady flow of revenue rather than a one-off purchase price. I hate it but that’s what everything goes towards.
I could see someone wanting to change their display glass and if that’s not feasible due to availability or cost I could see that as a valid reason for a new phone but I agree that the battery is by far the biggest reason to change a phone.
I use Arch (btw) on my daily driver too, but I recently switched to Mint on my server. Too much of a hassle to constantly update on Arch. Though I do miss the AUR.