Unfortunately that is because I am Canadian and use an American payment processor. It is certainly not my choice at all, it limits me terribly. Visa and Mastercard have insane rules, but I must abide by them. I can only process US cards, Canadians can do Interac, which is good for them, it keeps their privacy totally if that is a concern, people from other countries would be limited to mailing me a payment in an envelope to my P.O. Box in USD, which I seriously doubt many would bother to do.
Adult merchant accounts have all sorts of bizarre rules, especially when I am using a payment processor from the US and I am Canadian. To be able to process cards from non US countries, I'd have to get a whole other type of account in addition to the one I have, but I just do not have the volume of international transactions to justify the expense of it. Things are made a lot easier for ones that are US based, and "the big boys", sites like Xhamster (another Canadian based site with a premium level as an example) with offshore accounts, I won't bore you all with the technical details, as they are indeed boring, unfair and quite involved.
I know of a couple of other sites in this vein that are using PayPal under the table and against the rules, sadly it's just not an option if you do things above board and by the rules. I certainly wish I could offer that, it would be the simplest thing all round, but I cannot.
Ones if they are paranoid, worried about spouses finding out etc, can get pre paid cards and enter John Smith and a fake zip code and state. Some people I process cards for get pre paid cards and I just fill in John Smith, 90210, CA. They do not need a street address for pre paid cards and in fact if they do, it will not go through. If ones from other countries even try, it will just decline it, as I was made to block all countries except the US. Rules are often unfair, but we must abide by them for various reasons.