I think it's often either a need for attention or a need to disappear. Either way, it seems to come from self-esteem issues. I think apologizing as a tic or compulsive ritual is less common. I don't apologize unnecessarily in RL, and learned not to make it a feature of my communication because it is misread between genders in the workplace.

But in therapy, apologizing was often a cue to my T that I was feeling regressed, so it was valuable in his attunement.