I think it was because omegaverse was created to accommodate mpreg and possible femalexfemale impregnation. Female omega don't have just dick tho, they have both the male and female part. And from an explanation I previously heard, apparently the female alpha's Clit when erect turns into a dick apparently. Correct me if I'm wrong tho.
I don't have exact resources cuz I forgot the manga/manhwa that I got this information from but yeahh, I read a lot and ALOT of omegaverse things to find it out. Not all of them were nice tho, also extra info: if a dominant alpha ejaculates enough time into a recessive alpha or Bega, they could possible turn that person into a omega HAHAHA (๑•ㅂ•)و✧
If alpha women got dick, then why r omega men only fitted with a maigical ass and still have dick? Hmmmmmm??? Seems inconsistent