I don't know. Maybe I like first-person POV (both read and write) because the narrator usually sounds smart. How to explain? I mean I'm living in the narrator's head, experiencing what he/she feels, believing in whatever values are important to him/her. There is this very deep level of intimacy. Sometimes (honest), I don't know where I end and where the POV character begins.
That makes it hard to write a character as somewhat clueless if that character is also the narrator. It requires some level of detachment. Face it, is there anyone who is going to admit to being stupid, unless it is done sarcastically? Not that I'd not seen a self-deprecating narrator, but it's few and far between. Problem is, if the narrator is, in fact, not very bright, he/she is not going to know it in the first place. He/she will think that his/her believes are not wrong. (Unless he is sidekick #2 of a regency romance hero, or sidekick #1 of the hero's brother or brother-in-law, then all bets are off. But then again, this not!main character won't be writing fic in his point of view anyway because no one cares about the poor sidekick's skewed version of the events.)
(This is actually a very fast read. I suppose I could leave it uncut since it has nothing worth hiding. ^^;)