They do tie in in a way since if you're moronic enough to use a bank charging a foreign transaction fee, if you fall for the dcc scam, you're hit twice. First by the credit card processor (or the merchant) in using a rate above the interbank rate by as much as 5% and then the near criminal bank imposing a foreign transaction fee of 3%.

Now it really is a sticky wicket for the banks because one of the arguments of the credit card processors carrying out dcc is that it is necessary because mc/visa do indeed charge a 1% surcharge on the interbank rate for currency conversion and they and the merchants have a right to a piece of this action which is what dcc does. Besides, so they argue, if there weren't foreign transaction fees but only foreign currency conversion fees, it would all shake out pretty much the same in the end namely the credit card processor and by extension the merchant getting a share of the revenue from foreign currency conversion fees which the credit card banks (and mc/visa) keep for themselves. So, they argued, the banks had an unfair advantage and they were only attempting via dcc to even the playing field.

Officially, MC/visa claim they are opposed to dcc but because of litigation arguing what I just wrote above, they are forced to allow it. The credit card processors argue, naturally, that it is the banks who are ripping off their customers with foreign transaction fees and that if these didn't exist, the profits involved in foreign currency transactions could be more fairly shared by the banks, the credit card processors and the merchants. In other words, they say, don't blame us. We're entitled to a piece of this action. It's the banks that are the rip off agents.