So you admitted that people have succeeded in adding loopholes to the US government that makes all your argument no longer true, and you think they still should be allowed handle payment processing? To me it just sounds like you're arguing for transferring the power from one corruptible party (for-profit payment company) to another one (the government).
It would be easier for the government to actually regulate payment processors so they don't become so big that they can influence online stores that use them than preventing people in governments from turning corrupt and misusing the control over payment processes. Even then, the US government has failed to do the former, so how do we expect them to do the latter?
Well then, I guess you actually don't care that porn games are being removed from the stores right now because having the government be in charge will require you guys decades before such decisions can be overturned, just like how long the fight for free healthcare and sane gun control is taking in the US.
Maybe some governments are more receptive to their citizens plea than the US government, but most governments are definitely still in the pocket of people with big money.