There it is the big question. I mean the only females he's close to is Mrs. Puff and Sandy. And he would rather get a little to friendly with Patrick and Squidward.
Spongebob is just a kid at heart. In the movie they say this on many occasions. As you know it takes awhile for kids to start liking the opposite sex. And as a side note I don't enjoy the newer episodes as much. The old ones were great.