And they should be doing much more. Age verification should require a credit card. The idea that hardcore porn should be freely accessible to anyone (including children) on an anonymous basis needs to be put to rest.
It will also probably lead more men to pay for porn, since the companies running these websites will then make it one click.
Systems like Mozilla Persona would solve this on a technical basis, and was way ahead of its time, but there's no political incentive to standardise on something like this.
Maybe telling your partner that something isn't any of their bloody business is a perfectly valid thing to do, and an acceptable answer, even after, say, 50 years of marriage? It's a relationship, you are not a single conscienceness.
Personally, I'd argue having secrets from your partner doesn't necessarily make you dishonest. Lying to your partner makes you dishonest.
Anyway, my broader concern is I still wouldn't want my credit card company knowing my sexual preferences anymore than I'd want an ad company like Google knowing my medical status.
You write that neither you nor I should dictate what people share with their partners. I agree. I don't care what people share with their partners - that's between them and their partners. I don't think it's good for children to have 24/7 trivial access to hardcore pornography though and so I think we should restrict that and if that restriction changes the balance of what adults disclose with their partners that is up to those adults and their partners to handle. You seem to be advocating for policy based on allowing romantic deception - which is odd.
Finally, regarding your credit card company knowing your sexual preferences - I agree that it is a trade off but I don't think your, and others, addiction to pornography necessitates making pornography trivially available to children. If you have a better idea for how to age-restrict pornography I'd be open to it, but the defense that it would make acquiring pornography awkward for adults strikes me as pretty weak.
That may be a sound argument if it's one's partner who's bothered.
But what if it's your parents? If it's your boss? If it's your neighbours? If it's the local politician that you need to approve your planning application?
I don't know about ... but as a child my access to porn was rather ... limited ( to not say restricted ).