ENFJs don't like to talk about themselves. You can even see it on the forum, ENFJs are the NFs least likely to have threads going on and on forever about them even though there is a small but consistent amount of ENFJs lurking on the forum (hey yall!:hi

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I reveal myself to people who I feel comfortable with which is a surprisingly small amount of people. I certainly don't have this huge vat of secrets I'm hiding. ENFJs have that nice Fe covering so that batshit Ni doesn't come out clocking people over the head and scaring them off.
When you develop a good feel about people you learn what they're really interested in or what they're pretending to be interested in and you respond in kind. Pretending's not even the right word because that implies deception when it's not that. It's more like some repetitive habit we acquire when dealing with people. I say good morning you say good morning, you ask me how I'm doing I say I'm fine, I repeat the question back to you, you say you're fine and we're done. I know most people don't care what I did over the weekend or what I want to do with my life but they'll ask out of courtesy and I'm fine with that. I suppose having these jejune transactions with most people makes you more reflective than revealing and I don't doubt people can sense that.
And mostly, when I listen to people telling me about themselves I'm also figuring out if they're the kind of person who I'd want to share myself with. I'm highly observational of people through interaction. If someone sounds simple in the head (which I can usually tell after talking to a person awhile) I'm taking the information and making decisions on if I'd like to have a deeper relationship with the person. Maybe Substitute isn't so paranoid because I know I do it.