The question tells us that you’ve never made a woman achieve an orgasm.
The second half of female orgasm is internal, ergo the peen stand-in, but it’s not necessary. You can reach the same results without actual penetration.
I would assume that the fake peen allows both people to feel involved in the process.
Penis is just optimal shape for vaginal insertion. The lesbians aren't even real they are just ugly women, who don't want to settle for low status men. The bull dykes are often paired with relatively feminine bi-women, who are absolutely mentally ill.