Yes, when you "couldn't discover anything useful" when you pick the locks, the suspect has no valid alibi, so you don't need to ask the alibi question. It doesn't show up on the screen as a person with no alibi, though, so you have to write it down or remember it.
I love lock picking, perhaps primarily because it is so annoying NOT to have it. While I don't think it is as important as interviewing and evidence skills and Research, I do like to get it before other more "frilly" skills.
That said, it either gives you alibi information about the person whose house your searching or answers the motive question and gives you more suspects. This isn't always useful, as sometimes you won't need that person's alibi, and if you already have all the suspects, it's just a reiteration of what you already know.