Not sure, ask the people who buy AppleCare.

For me my iPhone is a work device as well as a personal device. Without it I would struggle to work productively. Therefore I pay for AppleCare to get my phone back up and running or replaced with minimal delay. Even if it was possible I wouldnt have the time, desire or know how to fix it myself. But that’s just me, each to their own.

It's a lot easier than it was to get Apple devices repaired without going to Apple.They now make the parts more accessible to repairers. Batteries are a good example. The new Spanish warranty law which extends the previous 6 month window for refund/replacements to two years will mean getting a swap without paying for Applecare will be easier.