There's a difference between people who may have at one point had homoerotic feelings early in life and those who are genuinely gay. Been a while since I've looked at the literature, but from what I remember in reading things like medical/psyche references, much of the research on up until the 1980s indicated that about 5% of the population self-identified as gay. Some sources suggested that this could be a low figure given the fact that there's stigma associated with such labels and, as best as I can recall, estimated that number to be closer to 10%. It wouldn't surprise me if the true number's a bit north of that. Frankly, 20-25% seems high, but who knows...
One of my crackpot hypotheses on gayness or other forms of non-heterosexuality is that it could be something that occurs naturally within the animal kingdom as a reaction to population pressure. If, for example, the human population were to become endangered, then assuming resources were somewhat abundant, there would be pressure to reproduce, and the species would need more individuals with reproductive capacity engaging in heterosexual reproductive activity. But in modern times, it's just not that necessary.