I wanted to say I think this depends on the people you're friends with and yourself, mostly. In my experience, if you don't open up, others won't as much, so it never becomes a deeper relationship. But then there's also just how people are and everyone is different. I am, or used to, be very curious about everything about others to the point I asked so many people questions that I would drive them away and now have developed a way of writing where I notably avoid questions when at all possible. It often was that I was far more invested in the other person's lives than they ever were in mine, in some cases I'd rarely ever get asked about myself even if a part of me really wanted things to be equal. But I wasn't honest about what I wanted so it remained that way until they left since there was no push to change how it was. It just grinded at me and now I have trust issues and am scared to start new friendships, though hopefully I won't need any since I won't be around long haha
Anyways anyways, I think what I mentioned above are big factors, some people just aren't wired to return the favor of listening or perhaps they were and stuff happened and they can't. And then aside from that outside factors come into play. Like people just get busier with life. Or maybe the situation where the conversation taking place isn't suitable for some topics. It could be any manner of thing. I would also just say I agree with a user above as well, if it's not going to make a difference and you plan on leaving life, it is easier not to have anyone caring.
I'd honestly ask so many things but I just can't bring myself to. I'd like to think I'm caring, but in many situations my fear and anxiety are stronger than my ability to reach out or inquire about others. I do love places like this where on discussions I can at least post somewhat more freely and honestly.