100% the trick is in the songwriting! When I was very young, I wrote songs for lots of local bands. None of these songs have ever seen the light of day outside the greater Philly area. But I play all instruments, and the bands I wrote for play all the instruments, some of them are currently music instructors even. It's totally the songwriting. And the gimmick too, you need a gimmick, which many of the not-hot celebs we are talking about in this topic have.
I was chatting with a pal yesterday about the fragility of the universe. If you know who is the Elton John, there is a dramatic story about him (go figure) before he was famous. He was living in the London with his fiancé (a woman!) and a pal called Bernie Taupin. If you know of Elton John, you know that Bernie Taupin was his songwriter. A genius. A master. Anyway, this fiancé was rich from her family, but Elton of course is a gay, and was trapped in his mind in this situation, engaged to a woman he didn't love and who would eventually make him stop his musical "hobby" in favor of being an inheritrix's kept husband. Plus again, he is a gay, so he was tormented by not being out and also about to marry a woman. One day in this apartment, he put his head in the oven and turned on the gas, intending to kill himself over all this. Either on purpose or by accident, he left the windows open, and never would have died anyway. His pal, Long John (lmao), came in and saved him. His pals Bernie and Long John counseled him, and he figured on not killing himself, not marrying this woman, and not giving up on his musical hobby. Bernie wrote Elton's song "Someone Saved My Life Tonight" about this story, and it was one of Elton's major hits. Imagine if Elton had instead married this rich woman, and never pursued music! Or if he had not been a drama queen and did the suicide right? How fragile the universe is!
What I was getting at in this non-sequitur is that the songwriting is the trick. Write a great song, and you don't NEED to be superhott or super cool. Think of all the dudes and chicks who had hits but are not exactly super attractive. Look at Jim Croce, one of the ugliest MFers you'd ever see. But that dude got all the ladies, because he was a master songwriter and then played those songs and chicks were flinging panties at him from every angle. You might not even be able to picture the face of the man or woman singing your favorite song when it plays on the radio at your plant. But you know the song, the words, the guitar parts, the drum parts, you could recite the song in your sleep. For Elton John, he had Bernie Taupin. For Jerry Garcia, he had Robert Hunter. Most of the top hits of the 70s radio were written by people other than the singers slash band. Carole King wrote 100 plus billboard charting songs, most performed by other people. The Beatles were such a hit (of course they were cute dudes that little girls swooned over) partially because the band had TWO of the top ten greatest popular music writers ever in McCartney AND Lennon. Lots of bands have a pal, or have one in-house band member as a great writer, but they had TWO!
All the ugly ladies we are talking about in this topic may owe their career to the author of the screenplay.