Why can't VAA accept Electron or Solo cards?

Just noticed that VAA don't accept Solo or Electron cards for payment. Anyone "in the know" care to explain why, or is it just an easy way to rip customers off with yet another fee and restricting choice to enhance revenues?
They generously point out that there are charges for payment by credit card etc; how else do they think (being realistic) that most people are going to be able to/want to pay?
They generously point out that there are charges for payment by credit card etc; how else do they think (being realistic) that most people are going to be able to/want to pay?