I've been talking to my therapist about something similar - masking, as someone else in the comments mentioned.

And one thing that I've been thinking about as a result is that I don't owe anyone my authentic self.

Asking me to reveal more things about myself is asking a hell of a lot, actually. So maybe I'm boring on purpose, because I don't want to get into an argument with a random parent on the playground, or a random stranger on a bus, or a random receptionist at the doctor.

I'll be interesting to the people I'm interested in, and boring to everyone else.