People straddle because they see pros do it on TV.
If a single play at a table is doing it (by himself) then you know something very valuable about the nature of his play I think. He is a gambler first. He will chase when he shouldn't. His range will be a most cards. Chances are he will love bluffing
and do it a bunch. Since he has shown that he doesn't really understand the idea of a straddle (which would be to get the whole table doing it) you can assume he might not think much about his play.