That's because there's literally no female LIs that are as unpopular as Jacob, regardless of the gender. Jacob was very unpopular with female and male players. It is likely that the devs thought that not many people would mind him not being an LI again. I can't blame them, the contempt toward Jacob ( and the results in the surveys were astonishing ) was so ovherwhelming that I'd think myself it wasn't worth it to waste resources for him lol.
I liked Jacob, but I hated, with a capital H the way they had Shepard talk to him like a cat in heat. That stopped me from continuing to talk to him for ages. I eventually wanted to see what it was like and just turned the sound off till later in the game. It was ok.
But I'm a die hard Kaidan fan, and since they didn't have any kind of DR, most all of my romances were with him. I did the others to see what they were like. I liked Garrus' romance but I adore him as my best friend who blows things up with me, and found Thane rather sweet. The one that surprised me the most was how much I enjoyed Jack with paragon Shepard.
I'm pretty sure I'll find all of the romances interesting. DA2 was my least favorite group, but even these had their moments.
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