Because making things everywhere compliant is cheaper than having both a non-EU and EU versions of software. See also: Brussels effect[0].
It's simple economics. The companies are also allowed to either do special versions to comply with local laws or even to pull out of the market. They just choose not to for reasons.
Sure, American courts ask for age verification, the entire world needs to comply now. Then people wonder why so much surveillance. You can’t see past Brussels effects, because ignorance.