I know SA does affect females more than males. However, I remember reading how many of those same females often end up in relationships based on more outgoing guys asking them out, etc. Meanwhile, the guys with SA remain single until they're either approached by a girl or they do likewise.
I have looked into this some more. I did find a few things. This is not in the order it is on the site. Here is some info from a site that reported on love-shyness for males:
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Gillian Butler, a clinical psychologist and the author of Overcoming Social Anxiety and Shyness, says: “There’s lots of advice for women about how to get over shyness, but shyness can be much harder for men to deal with because it’s seen as a feminine trait.”
The problem, says Gilmartin, is that, according to all social rules, men are supposed to approach women, so love-shy heterosexual men fare badly. In women, shyness is seen as an attractive quality, but if a man is too shy to initiate a conversation with a woman, his chances of a love life are slim.
Because love-shy men can’t be officially diagnosed, no statistics on the incidence of LS exist. Love-Shy.com has more than 500 registered members. Gilmartin studied 300 men aged 19-50 who conformed to the love-shy criteria, comparing them to 200 non-shy men, and concluded that LS affected 1.7m males living in the US — about 1.5% of the male population, which seems incredibly high. “They suffer from an overactive limbic system, which is the emotional brain.”
According to Gilmartin, shy women are as likely or even more likely due to their love-shyness as non-shy women to date, to marry, and to have children, while this is definitely not the case for heterosexual men.
Gilmartin argued that love-shyness would have the most severe effect on heterosexual males, because of gender roles. This is because heterosexual men are almost always expected to take the more assertive role in dating situations and to be the ones to initiate intimacy with potential romantic partners, whereas heterosexual women generally take the more passive role, as assertiveness on their part is far less crucial in successfully developing a romantic relationship.
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That last paragraph tells the whole story. Shy men are so often single because of gender roles. Men are expected to be the asserters and women are allowed to be passive. It's been like this for centuries, not much has changed and it won't change any time soon.