If I put petrol in my diesel car it'll screw the engine. If I had some kind of electronic sensor preventing the engine from running if it detected petrol it would save me loads in the long run. Same with the fuse in my plug preventing my gear from getting fried. When my credit card breaks I get the issuer to send a new one, there is no way I'd trust some talented Indy to fix it.
This is a safeguard on my precious digital data.
You guys would be frothing at the mouth if iOS security especially fingerprint security could be compremised by just changing the screen. Stolen iPhone with Apple Pay and 5 cards registered, hacked by changing screen or sensor, that'll close apple pay in a heartbeat and sink all mobile pay solutions.