Well, firstly if polls are an indication of how much content a character should have, if we take the poll in this thread for example being in first place with 24% doesn't mean that the majority of players like her best. Quite the opposite: 76% of people like some other character first. My favourite character is Emily, but if I can't have Emily scenes I would much rather have scenes with literally any other character than with Ann. All the other characters combined don't come close to 76% of the scenes currently in the game. Not even close.
Currently, there are 57 scenes in the game's gallery, out of which 26 are with Ann if I'm not wrong. Way over 24%.
19 scenes with Vannessa.
12 for all the others including 5 one-off scenes with secondary characters, which leaves 7 scenes between (for me) the best three girls: Alex, Emily and Jenny.
(I've checked it and Alex photoshoot scene isn't even in the gallery, so let's make it 8 scenes between the three of them out of a total 58.)
Proportionate? I don't think so.
Secondly, I'd love to see another poll asking "Who's your least favourite girl?" That would be interesting.
Finally, and this is something that has been discussed a lot here, people who like Ann primarily do so because she plays a certain role in the story they have a fetish with. She's the nerdy girl they can corrupt, share and turn into a filthy whore.
If Alex played that role, she'd be their favourite. If Amber was a main LI and she played tha role, she'd be their favourite, etc.
And very importantly too: you get more fans the more screen time you get. It's not fair to compare her popularity to anyone else's.