In games (especially interactive adult titles), it’s technically challenging to depict human skin realistically. That's why designers mostly take the simpler route by making genitals look smooth and monochromatic.
Unfortunately, this causes players to subconsciously treat this simplified image as the gold standard. What some call 'disgusting' is actually a norm. A grown man’s organ isn't supposed to look like a porcelain toy; veins, skin folds, and natural pigmentation are the biological mechanisms that make sex possible and pleasurable.
Furthermore, the option for penis customization was previously included to a vote for patrons, but it didn't receive enough support to be prioritized for implementation at this time.