More girls means more popular.
More popular means more people like you.
People like you because you’re nice.
You are nice, and good and therefore worthy of getting married.
Ergo having a lot of girls at your wedding is a validation of the kallah to her mother-in law that she is worthy of her son.
Personally, I find the less girls, the more fun the wedding is. The kallah gets to actually focus and talk to her friends instead of making sure she dances with everyone, or everyone edging themselves out to be sure to dance with her. The dancing is more intense because it’s a more intimate crowd. The people who are there, are there because they want to be there, not out of obligation to an old high school chevra that is long extinct, or product of a small seminary.
I have two weddings in mind of two friends, one massive, the other tiny. Hate to be rude, but the small one was SOOOO much nicer, even if the massive one had better food, a better band, and better dressed people. The atmosphere was so different based on the amount of people there.
I know my wedding is going to be one of those massive ones, because my family on both sides is HUGE, but I do kinda wish I’d have a small one, where I can talk to my friends and close family without being exclusive…and without having people stick around because (whisper) “there are no girls…”