I don’t think it’s only introverts who will agree that one can only have so many “close” friends. That number may be different depending on the person, but there is always a limit. The human brain simply can’t keep up with more than a handful of truly close relationships.
Introverts aren’t usually anti-social. I, at least, like to do things with my friends. The key word there is “friends.” I don’t see the fun in going to a party full of strangers. I likewise don’t see the fun in going to a party full of acquaintances.
Best friends are what I thrive on. A select few who can have fun even when doing nothing. Who understand you and don’t judge a sweatpants day. Who will talk into the night about strange and wonderful things. Why is blue such a popular favorite color? Why do weather vanes exist–for tornadoes, originally? Why are tomatoes and potatoes named so similarly when they have nothing in common?
Without these thought-provoking topics, conversation loses its sparkle. Introverts love to think, and they do so constantly. It doesn’t have to be about “deep” subjects or personal things, just something they can add to. Introverts can’t talk about what weather we’re having, but most would love to talk about how, theoretically, the Earth would function without any weather at all.
Unfortunately, it takes a level of trust to get to a place to talk about this sort of thing. And to get to that level, one must first talk about the weather we’re having. Thus is the friendship dilemma.