Carriers have been blacklisting IMEIs for at least 10+ years. Since phones tended to be carrier-locked back then you couldn't go to a new carrier without being in good standing to get your device's unlock code from the old carrier. Now that devices are available unlocked by default, it is probably harder since it would require carriers to communicate IMEIs?

Not sure, I think that there are international lists of stolen IMEIs. Maybe it's just in Europe, though.

~15 years ago the blacklists were certainly shared within Europe, but there was an intercontinental trade of blacklisted phones from Europe to Africa (and, if memory serves, Asia).

I looked it up. US Carriers were forced by the US government to start blacklisting them in the final months of 2012. They didn't do it voluntarily.

Australia had been doing it since 2003. IMEIs have been around for 30 years? Everyone having a cellphone is still a relatively recent phenomenon, but according to Pew 80% of American adults had cellphones for several years already before carriers were forced to deal with stolen ones.

I believe the point is that they could've been blacklisted from the start and instead carriers would just put up their hands say "there's nothing we can do" despite there being something they can do.

It's like when your apple laptop gets stolen and then starts using your applecare support and apple won't help you get it back.

Of course, if you decided not to pay your phone bill I'm sure that device would get blackslisted real fast.