Emma's model (called precisely Emma) has been around since Genesis 3, and it's a great model to work with, so that is the reason it's so used. You aren't the first player who talked about the overused models, but I have to say that I have played very few AVNs, so the chances that I have seen any of the models are relatively low. I'm sure most players have played more than 8-10 AVNs, so they will have seen many more models than I have.
I find her lovely, but I understand your point. If you have seen her in 35 games, it's difficult to get attached to her...
Or not, I've found lovely Charlize Theron for the last 25+ years and 40+ films
We all want our girls to feel unique, so if I know X girl model is being used in 47 other games, I won't use that model. The problem is that, to detect it, I should play those 47 games... and remember the girls after it.
Variety is the keyword here.
I understand why so many devs have their girls totally shaved (tastes aside) as it's easier to pose them and use some clothes; it's also faster to render.
There aren't a lot of full bushes hair models on the market also, and the ones out there have some problems, like not following the labia movement. For Alexia, I had to use three hair assets simultaneously: the upper bush, which doesn't cover the labia, and two assets that cover the labia, but haven't as much hair as I wanted in the upper zone. I'm happy with the result.