This is done by organized crime with engineers on staff. Sure it’s drug addicts stealing cars but the people shipping them are smart and have access to capital.
People will buy a $150,000 SUV for 50k and they can still make money. Phones have less incentive and Apple is going to be better at bricking the phones than carmakers will.
I suppose organized crime doesn't systematically take advantage of that because cheap phones are cheap, and the people who own them are poor. You don't get that much benefit from pwning them.
Alternatively, maybe organized crime does take advantage of them but we haven't heard about it. They could have a giant botnet of them for all we know.
I still see a lot of iCloud phishing messages, but also understand that Apple has made this vector harder.