Enforcing laws against porn companies distributing porn to minors seems reasonable. It's already illegal many places, such as the US. It is then their responsibility to gate by age. It has always worked this way for liquor stores or basically anything else age-gated, including some online services like poker. If you dont want to provide age verification you don't have to.
When I buy liquor (well, I don't drink anymore, so THC seltzers), the liquor company isn't saving my ID to my profile and then following me around everywhere I go for the rest of my life shouting "This is MALFIST, he's 42! He buys alcohol! He also visited X Y and Z last week and had interests in A, B and C. He's annual income is six figures and buys expensive bourbon."
You can absolutely buy for instance tobacco, cannabis by the pound ("CBD" but actually ~20+% THC[a]), explosives(tannerite), alcohol (wine), and guns (black powder, or perfectly functional cartridge pre-1898) completely legally online without ID check. It's really not a problem, which is why most people probably haven't heard of it being one or even realize all can legally be bought online without ID.
There is a difference between a liquor store checking your ID, and a liquor store scanning your ID, appending it to a record of your purchase, and uploading it to a service to be processed by third parties (such as insurance companies, perhaps).
(In the US, the latter occurs more often than you may expect.)