If you don't leave junk it won't cost you much. I really don't see this as gatekeeping.

> one of the few that can even afford to pay it. Like when Amazon finally had warehouses in all fifty states and suddenly quit campaigning against online sales tax.

That's not accurate at all. They could always afford to pay it, and so can other companies. What changed is that they stopped counting as "online sales tax" so they didn't care about those laws anymore.

If they could get out of sale tax, they very much would still want to. If they could get rid of sales tax for everyone, they would be for it. Sales tax isn't benefiting them by acting as a gatekeeping force.