Earlier quoted context omitted.
Or indeed care about the law enough to bother before they're fined for doing it. After all you'll need to prove they didn't delete the data first!
The GDPR penalties can reach 4% global (i.e. sum all related companies) annual turnover per infraction . If anyone ever found out Facebook had a widespread violation, Facebook would be likely be dissolved.
Nothing of value will really be lost, replacements would spring up super quickly and I'd like to think that we would have learned enough about the downsides of the current social-network systems for the next generation to avoid the pitfalls and hopefully make something much better.