And people with social anxiety don't want to take risks that could result in increased happiness/relief from suffering, but which also have the potential for greatly decreasing their social status.

Examples of such actions: romantically initiating (see "Lesbian sheep syndrome"), asserting one's worth in interviews (= a non-negligible part of the wage gap, after materity effects are removed), "saying no" to unwanted advances, and... committing suicide.

(Fun corollary hypothesis: anti-depressants like SSRIs increase suicidality precisely by removing the inhibitory effect of social-anxiety upon this class of positive-utility-but-disapproved-of actions.)