I feel like Cammy or Nina Williams are far more iconic in gaming than Mai.
Mai's only really noteworthy because she's skimpily dressed and has giant boobs.
Edit: There's also Sonya Blade too.
I was trying to not pull too many characters from one franchise, but I agree that Cammy is up there wih Chun Li. Disagree with Nina Williams in comparison to other fighting ladies, though she is up there too. I completely forgot about the MK ladies which are also quite popular, like Sonya and Kitana.
As for Mai, why she's popular is irrelevant to me: all I know is that she is the face of advertising when it comes to KOF and splattered everywhere, which was popular in the FGC and seemed to be a rival of sorts to Street Fighter, and seems to be very popular gaming lady even to those who've never played an SNK game, and is often compared to Chun-li when it comes to Japanese companies original fighting ladies. With that said, I wouldn't believe for minute she would get in Smash nor care one way or the other but the only characters from KOF that can possibly exceed her popularity are Terry, Kyo and Iori, which are all males.
I bring this up because I told that to one person and I was called homophobic.
You were accused of being some sort of bigot because you found a personality or quirk to be aggravating? Bizarre, but can't say I'm surprised. People are very quick to label.
I wouldn't worry about it. There is nothing wrong with finding a personality type annoying. I'm sure everyone has that one type that they dislike. Just browse through tvtropes you will come across tons of them.
She's still a female 3rd Party character, who if got in would be an equal part of the character to Banjo.
But Kazooie isn't really noteworthy on her own, nor is Banjo on his own. It's the pair that makes "Banjo Kazooie" and it's what people find endearing about them. No one brought up Kazooie because alone she feels incomplete.