To be clear there were female saiyans none of them are alive but they existed. To use the TV special as an example involving Goku's father. Bardock had a female team-mate who was a saiyan. The reason for none in the manga was that only a few Saiyans survived all being male. Because it was Toriyama's choice to have it that way. Remember Namekians were the species that had no females because they reproduced Asexually.