I hear you about having no interest in seeing a guy shoot his wad. But isn't that generally why one *exclusively* likes oral scenes? I'll go out on a limb and project, based on many years listening to the complaints, demands and rants of porn fiends, that guys interested in seeing copious amounts of cum, blowbangs, bukkake, gokkun, etc. break down as follows:
(1) 80% straight guys who are simply into lowest-common-denominator whore degradation.
(2) 10% guys who are gay and maybe don't know it.
(3) 10% bisexual guys into mucho cock and jizz.
Kind of obvious, really.