I don't say it as a plea for recognition, reciprocation, or negotiation. I say it in these circumstances: (1) The feeling wells up in me and I know the other person won't freak. (2) It's true and the other person wants me to say it (either because it's a ritual to say it at certain times, or because zie's making a plea for recognition).
I personally don't say it directly to another person when I believe it's unreciprocated, because I don't enjoy the processing and explaining that has to follow. (If I believe it's reciprocated, then I'll say it and do the processing.) But one big change for me over the past little while is that in such cases I will say it to myself. In the past I was insistent that the word love only applies to a reciprocal relationship, so I would deny I loved someone if I believed zie didn't love me back. I'm so very glad that I've gotten rid of that policy.
On the other hand, even though I don't plan to start saying "I love you" to more people, I think I probably should make more of a point of telling people that I like them and what I like about them.
Only you know what? I have gotten out of the habit partly because I've gotten the impression that some people are embarrassed when I tell them what I like about them. Maybe when I'm in that mood, I do it too much. Or maybe some people don't like praise, or don't want it from me, or think I am asking for something in return. And actually, although I'm not asking for something in return when I tell someone I love them, I sometimes am asking for something in return when I tell them I like something about them. What I want is for them to like me back because they see me as a person with insight and good taste.