> In a physical store they're neither de facto nor de jure required to check your ID when you're clearly an adult, and many of them don't. There is no feasible way to do the same thing on the internet so instead it effectively becomes requirement to ID everyone, which is different.

1) Not true. The burden is on the seller to verify age. Sure, they can try to do it visually but if they fail they are still liable.

2) Even if true, nothing changes in a legal sense if they lose the ability to informally verify age because thats not a legal right of the consumer. It's just an incidental feature of buying in store which some people value. There may be a difference there, but its not a legal one.

3) Texas law didn't mandate age verification by ID specifically.