I have gotten them from who only allow friends to VM back leaving me a harder time to communicate with them when a simple 'like' would help. I had a long two day delay to reply to one more then once because of this-- a 'like' would have helped a lot there... I have to pm them or ask for a friend...
I use them as acknowledgement of this I like, funny, well written or just agree. It can cut down on unneeded posts, and easily get in on a conversation with out butting-in. So being able to do that more just seem helpful for me. But I get you don't have a use for it, that's fine :)
They kind are but personally I have gotten them from who only allow friends to VM back leaving me a harder time to communicate with them when a simple 'like' would help. I have also seen awesome VMs I'd like to comment on or give a little 'like' but can't easily as no one other then the two...