If you work at Subway making sandwiches your preference may be to serve kids, because usually they just want meat and mayo. But when that Walmart fat guy walks up and you know in your heart he wants everything, you smile and make his sub all the same.
Their preferences are important but as a good business practice you serve all comers so long as they maintain the rules of the establishment. If that makes sense for ya.
Personally as a single guy I can see advantages to both. Married men may be more discreet, single guys have no vengeful S/O.