Probably for the same reason they didn't exclude Five Eyes from SWIFT when they invaded Yugoslavia, Libya, Iraq, Afghanistan and Syria and killed over 1,500,000 people in just over twenty years...lol nah it's about money. They'd shoot themselves in the foot if they did it.
It was much more than just the Five Eyes countries involved in those invasions, so there really wasn't anybody of any significance left that could have removed them from SWIFT.
That is exactly my point; you don't dig your own grave. Sanctions are only affective when it hurts someone else, not you. That however proves to be a difficult task in a globalised world.
