d) why would anyone try to steal a bike that is going to be seriously
damaged and become worthless in the process?

Because it can!

Thieves and the assorted scum do not think like you. If it is there
and there is a chance of stealing it then it 'must' be stolen! Failing
that it 'must' be damaged to deprive you of something that said
assorted scum could never legitimately buy.

It's sad but that's my view on it. My best bike is only ridden and
never locked anywhere (save in the shed). If I go somewhere where I
know I have to leave the bike unattended, but still locked, for some
time then I go on my skip-saved hack bike.