I don't understand this. In the American startup I'm working we're extremely careful with respectful data practices due to ethics and GDPR (we have a lot European customers). Why doesn't Amazon give a shit about GDPR? Do they have a leverage?
I would assume perceived toothlessness. A better question is why should they? Or else what? Is that "what" absorbable by them to not eagerly spend a bunch of money and be shown to kowtow to governments making very large internet laws? Can they just pay it some lip service for now like their peers?
If they don't choose to put themselves somewhere, everyone may go after them separately.
If they weren't an EU company they couldn't take advantage of Luxembourg's tax laws. So it follows that they have to follow all EU laws. Because they're incorporated in the EU.