And science says there is a good reason we do it.
"Over 50% of women report having faked an orgasm at least once in their life, usually to satisfy their partner. Why should a pretend orgasm be pleasing for the man? The current belief about the female orgasm is that it evolved as a way for women to separate the men from the boys. Men with good genes – who were more attractive in other words – give more orgasms. Muscle contractions that take place during the orgasm help move sperm around to where it can more easily fertilise the waiting egg. This idea has become delightfully known as the ‘upsuck hypothesis.’ So for the men, ladies should always come first. " read more
Immediate problem being that physically great men worked for thousands if not millions of years. Today brains and luck brings more wealth.