I kinda meant laws. You can control/police someone more easily if they live in your country.
Some areas like Scandinavia have done well to police online webservices like amazon (by banning some of their operations - example below) but they still don't have much control other than completely blocking them or completely allowing them. I think the US could directly pass laws on amazon's working conditions too for example.
Example - Iceland and Sweden require a democratic union to exist for a company that takes on employees there. Amazon don't want to have to deal with this and thus have to rely on other countries' distribution centres and postal systems in the nordics.
If bezos moved amazon to the Netherlands and started allowing cannabis to be sold internationally, it'd be more difficult and delayed to try to ban this than if it was still headquartered in the US.
Someone mentioned a wealth tax not working in France and that was probably because people can just hop country within Europe and kinda internationally too.