I don't think they have at all. All I've used them for is to gain a general idea of who a person is. And by that I mean, like general, usual behavior. Patterns. 'Cause really, that is all the MBTI is for. So I might go, for instance, if that person's an INTJ, "Wow, they might be touchy. All INTJs are a little touchy and insecure. I should be careful around them and not say anything I don't mean, or joke unnecessarily." And of course I don't go around typing people. I do that if I'm bored. But if I happen to know the person's type or if they've told me, I'll keep it in mind about them.
I think really, that MBTI is like a personality type within a personality type. The fact that you took the test that day tells something about you. I don't know what, but it does. And you get a result. So how will your reaction be to that result? Will it be good, bad, ugly even? Will you have the courage to type as a sensor possibly? I wonder. It's really interesting. Because it's like a super meta test or something.
I wish someone would discuss it with me, though. That's one thing I wish. Like, a super in-depth discussion. That'd be nice. And I'm kind of always wondering, "Do you know the MBTI? Do you?" about other people. Because it's one of my favorite subjects. But I don't push it on anybody.
One thing that drives me nuts though is that I don't know my type. Like people will say, "Yeah, you're an ISFJ." But I'll be like, I got really attached to ISTJ and I thought that was right. Fe doesn't sound right for me. But eh, whatever you see in me I guess. I think that might be a common problem in the community, actually, that you get attached to your type and can't see anything else once you've memorized the description. You might be off by one letter but will argue people until they're screaming that you're an ISFP, not an INFP. Like okay. Like for whatever reason you like that type description and don't want to budge from it, even if another might fit you better. Like you like the artist stereotype instead of the sensitive wallflower one they present. Hmm.