1. The two Negativist Ejs (LSE, EIE) are decently likely to be somewhat socially isolated, and LIE is an Intuitive type so they can often be interested in sort of esoteric things (a lot of literal esotericists are actually LIEs, although it still is mostly dominated by ILIs and EIEs). ESEs can also be interested in typology because really lots of people use typology as a conversation topic (that's how I got into this actually, although I'm pretty certainly not ESE) the same way they use Hogwarts houses, Pokémon Go teams, astrology signs, and things like that generally, although I guess really socially introverted (as opposed to socionics introverted) people don't tend to be exposed to that so much.
2. Socionics was invented as a sort of sociological and economic theory (socionics = social economics), not for self-discovery. It focuses heavily on relationships and observable behaviors and there is a decent amount of material out there about applications (some of which is pretty sketchy). Out of all personality typology systems, socionics probably attracts the most Ejs (as well as Eps, since I don't see them fiddling around with the enneagram too often either).
That being said, even if there are legitimately more Ips interested in socionics than any other temperament, it's still not great to assume that people are Ip until proven otherwise since at least most of the people on the "type me" thread who leave right after tend to be pretty equally distributed like in the general population. The people who stick around might be more likely to be Ip, but based on the regulars here, not overwhelmingly by any means.



