Drills, Wrecking Balls, Forks, Explosives, Mechakoopas, Propellers, Tongue, Hammer and Kart Mode...Clown Car has a much more "Smash" feel than Daisy, who's mostly unarmed for a good majority of games she's appeared in, only ever using stuff that everyone else has access too because it's just Sports Games, and when it comes to the Sports Games, Waluigi is usually the preferred "Mascot" because of his infamy and wacky charm. He's just more...likable, I guess. He's been fleshed out a ton from Spinoffs whereas Daisy hasn't really changed at all since Party 3 aside from visual design, so...
As I said, Daisy is just sortof...outnumbered. There are people who do her job and there are others who are just more important to the Mario Series (Such as Rosalina and, yes, the Clown Car) since they're still out and about in the Mainstream Mario games.
But that's just my opinion on things. Opinions aren't facts, so take my words lightly.

Hoo boy, where do I begin.
Clown Car over Daisy: Yes. Read above. It's not because I hate Daisy, it's just that Clown Car fits more in a Fighting Game because of it's arsenal, piloted or not.
Completely Hated: No. Infact, I love Daisy. She's my second favorite Mario Character, with Yoshi being Number 1. She's pretty awesome.
Infact, why does one guy saying that he thinks, in his opinion, that Clown Car suits Smash more than Daisy immediately make the entire fanbase think the same. I don't geddit.
Just because she's a girl: Should I even comment on this
Princesses are Useless: Peach, Zelda and Rosalina ain't useless, so...
Princesses are all the same: Peach is a Damsel but has hidden powers, Zelda is the psychic, Rosalina has the Lumas by her side and Daisy has Flower Power (albeit we've only ever seen it for very little occasions, she's very out and about on what she represents despite being called Daisy, lots of folks give her a relevance to Fire because of her Desert Heritage and some use the Crystals she has from Strikers Charged as a thing)
They ain't the same.
More Males than Females: I feel as if this isn't because your claims, but moreso because there just happens to be more male characters in gaming. Yes, there being only 3 Females (Jigglypuff could bring it up to 4, Black Mage is ambiguous and Chibi Robo's a genderless, up-to-opinion robot so they could count too if you consider Cheebo to be female, so all things considered there could be 6 currently) but that's mainly because there isn't really that many in the first place.
Peach, Daisy, Rosalina, Zelda and Samus are the main Nintendo females I can think off the top of my head. A whopping 5. It's not the fact that we dislike them, there just isn't very much of them.

Now could you please calm down?
You've already been kicked out of Smashboards iirc so I don't think it's a good idea to get all bothered over this lest you get kicked out of here, too.
If I sound harsh, I'm sorry, but I don't want you to get the boot.
We cool.