SamTherapy -

Not enough of a market to make the effort worthwhile, I would bet.  When all is said and done, the majority of buyers want pretty models with an average feminine appeal rather than female body builders. 
I took a bit of a risk with my female robots but they're reasonably popular.

Thanks for telling me that. Pitty though, I would pay for a realistic fbb texture and I wager that there are more Poser/female body builder lovers out there than you suspect and they would all come out and buy it if a realistic FBB Poser texture were on sale.