Where's the profit.

One must be a realist. If there is no profit motive, it won't happen. Ever.

One profit motive is "the government has regulations, I will be fined if I don't do this".

Another is "my competitors do it, and people buy their stuff because of it".

All the technical solutions are easy. And you're right, it's not about age verification, it's about profits.

The same way cars are regulated to have air bags, couches be made from non flammable materials, and so on.

Human nature has been the same forever. It will never, ever change. Ever. Profit drives all.