I mean no one should take that poll to serious and in the end the answer with by far the most votes was "harem" anyway, as it should be.
The truth is that I feel both Dalia and especially Penny simply hadn't much time to shine so far. Dalia had her competition which was nice, but not too special and Penny had that touching memory and the Halloween party where she was gone for a long time, so we could've awesome and funny scenes with Nova instead. Penny got mostly outshined in what originally seemed like it would be mainly her scene.
Both lack a niche they can call their own, in my opinion. Yes, Dalia is the sporty one but that only really shows with her having slightly more defined abs than any of the other girls. Her big conflict is that she is only the 2nd best woman in sports in the city...damn, what a serious problem to have...
Penny on the other hand is supposed to look a bit more like a blonde bimbo but is actually pretty smart. But that only comes through here and there and in the big boob department her mother is right there with her anyway, also bringing the red hair and the potential milf appeal into the mix. Her internal problem is that her good looks kinda outshine her intelligence and that people are very superficial in regards to her. And again: "I'm looking too good!" is another serious problem, a lot of people can very much relate to...
So ultimately it isn't too much of a surprise to me that those two are probably the least favorite LIs in the game so far, because they both are comparatively boring to begin with AND they haven't been to fleshed out either. At least as of now neither of the two really had stand out scenes as far as I remember, with the exception of Penny's memory I would say.
And no, I don't think either of them is unpopular that would mean that people actively don't like them and rather would them see gone from the story. I think that most players don't care as much about the two as they do about the others like Luna, Alex, Annie or Nova mainly.