Bitcoin is not viable due to it’s high transaction fees and low transaction rate. Some random Alt coin might work, but getting PornCoin adopted is difficult.
You don't have to have PornCoin, they can use an exchange like Binance which has a lot of different currencies supported, and the customer could pay in any one of these. Or they could use Request Network if that pans out.
And lastly, Bitcoin fees currently aren't large and you can get a confirmation with a few cents fee. That might stop being so if it becomes too popular again, but if off chain solutions like Lightning Network pan out, then that'd be sorted out.
For the average person to buy something you need to buy a coin, that's 1 transaction on the block chain. They need to buy something with that coin that's transaction #2. The merchant needs to sell that coin that's transaction #3. Granted #1 and #3 can be much larger reducing the costs, but the average user is likely to be splitting #1 across a small number of transactions.
Further 2 exchange fees sit on of those 3 coin transactions.
In theory you can have an exchange handle all 5 of these transactions, but then your using the exchanges book's not a block chain.
