The stats are actually pretty clear. T-mobile in particular got hit with plenty of fraud and others did too before they got better at locking things down.
Activation locks were also a control put in place to reduce what was for a while an epidemic of street crime where phones were stolen. The locks are critical and pretty popular, many DA's and cities demanded Apple put them in to try and reduce street crime - and they did.
So the idea that locks prevent theft / crime is not completely invalid. In fact, there are laws against stealing from houses and many people still lock their house. Their are laws against steeling cars and people still use keys for their cars.
It looks so unsecure. It will be much better if Apple will lock your house and car instead, so you will just ask Apple to unlock your house. If you violate Apple rules, e.g. by storing inappropriate content in your house, they will just ban you, so your city will be a much better place to live.
To be fair, the fact that they signed a contract saying they would pay for the phone is what's supposed to be what keeps them paying for the phone. There's already laws around paying for things you buy, so the whole "well, people wouldn't pay for their phones" argument is completely invalid.