I have my own theory on why many Schizoid Males lack a "significant other." I believe it is, simply, that many of these men know that most women don't look good without makeup on. What they want is to see a woman with no makeup on. They feel like the women are hiding something/being deceptive when wearing makeup. Since they hardly ever encounter a woman with no makeup in "everyday life", their chances of staying single go up (due to the "numbers game" and the fact that these makeup-less women don't usually ask out Men).
It is also my belief that many of these men are vulnerable to episodes of "schizoid exhibitionism" where they have some dating phases in their lives (though not all Male Schizoids do go through dating phases). The "schizoid exhibitionism" dating phases are induced by the constant, everyday bombardment of women who seem to be deceptive/fake by wearing makeup. I believe this is almost like a defense mechanism or counter to what they see as deceptive behavior.
Anyway, just my theory on why SOME Male Schizoids lack a "significant other". Feel free to chime in and formulate your own theories on this topic.