I don't hear it often, and only when I say it first. I wish it were more often, and yes, I think it's because there are issues in our marriage.

That said, everyone is different. One of my friend's husband says it to her CONSTANTLY. It almost seems like punctuation for him. Like, we will be somewhere and he gets up to go to the next room and says "love you!" in front of everyone before he leaves, even though he's coming right back. And after every mundane phone conversation. They do seem happy, so I'm glad it works for them, but I wouldn't like that.

I am with the others in not being able to imagine that OP. We express it at least a few times a week. If you love him, start saying it and see if it is reciprocated.