It's not about "having to" replace parts. It's for just-in-case. It's essentially insurance.
The battery in my M1 MacBook Pro went bad recently. But I have AppleCare, so I was able to walk into an Apple Store and hand it to someone, and the next day I picked it up all repaired. (New keyboard, too, since the keyboard and battery are considered one part.)
Total cost without AppleCare: $250 + tax.
Total cost with AppleCare: $0.
Total I've spent on AppleCare: $150.
If I had some machine from Dell or Acer or even Microsoft, what would I do? Ship it back to China for six months? There's no store I can walk into to get it fixed the next day.The value in AppleCare is the same value you have in fire insurance. Maybe you want to save a few bucks and take your chances that everything you own won't burn to ashes and you have to start over with nothing. I'm not in college anymore.