Just to stir the pot and hopefully facilitate a deeper consideration, you might consider the thing-beyond-the-thing. By this, I mean the thing(s) that the interaction leads to, which can vary quite a bit depending on the setting and who you're interacting with.
Interactions lead to romance, business contacts, friends and acquaintances for specific things (poker or board games, fishing, hiking, etc.), general purpose friends for hanging out, the list goes on. My point in all this is that interactions, for you, come at something of a cost. This leads you to think that it's not worth your time and effort/discomfort - and perhaps it isn't. But it cuts you off from the second, third, and subsequent orders of effect - and those affects might be very much worth your time, effort, and discomfort.
Hope this comes across well and not preachy. For my part, I love meeting new people, meeting old friends, etc., so of course I am biased.