Why is it difficult to avoid trying to solve other’s problems during a conversation? what can you say instead of offering advice?

There is something called empathy, this causes that we "share" emotions with others.

If we see someone that is having a problem and is suffering, these emotions will affect us, and we do not really want that, so we will try to help the person to solve the problem, not only because we want to help, also because it will make us feel better.

If you do not have any advice you can always offer your time and company, most of us usually can't really help or give good advice, but the presence of a friend/significant other is something that helps in a lot of situations.