Even if you have no connection to the group, someone in the group may have with you. Plus, someone in the group may have bigger abandonment issues than you can realize...and need to know that THEY aren't the one who made you leave, you know?

It's also good to do this out of respect, imo. They are ppl...just because you are making other choices doesn't mean you have to just sneak away silently...

It will also help you formulate why you have chosen to leave (help you put it into words.)

Hope it works out for you