Actually it is , i'm talking from experience since the character i used as an Example is a favorite of Mine. Much like Jill , Claire is appealing and the fans know it , but they like to Show the love for them starting with the fact that they are a Strong role model for females. Why do you think Rebecca is not as popular yet she is still Pretty and all?? Because many see her as a ''Weakling'' and a side character with zero Strong points , unlike Jill and Claire. This means fans care more about what they represent rather than how they look.
There's literally lewd material to every character out there and more if they are Female (real talk) , but then again i have not seen many people listing ''Hot'' as the reason why they like Mario , Luigi , Daisy , Wario , Peach , Waluigi and so.
But For Rosalina , it seems like the auto-answer to this question provided by many people.
This kind of talk is something i see in a daily basis:
''Rosalina , Hot, Rosalina , Biker Suit, Rosalina , Hot , Rosalina , Lewd , Rosalina , Sexy , Rosalina , Smokin- Hot , Rosalina , Biker Suit , Rosalina , Milf , Rosalina, waifu ......''
i would like that to be a lie , but it is not.
You would rarely see something like:
''I like Rosalina because she is a Strong Woman amount the Mario universe''
'' I like Rosalina because she is motherly and mature unlike others''
'' I like Rosalina because she can float and has magic powers''
'' I like Rosalina because she is gentle and caring with the Lumas''
This , right here , is something that almost no one says anymore.