It's not a virtue signal so much as a cope. They are afraid to leave these people because they would be lonely, or afraid of them freaking out when they left, etc. A weakness and just plain old human affection for people they love. It's also hard to find non-Lefties to replace them with, seeing as so many are Leftist now. As an introvert this doesn't really effect me but I could see how more social people would find this troubling.