There are so many factors that could be the cause. Things like cultural acceptance, generational gap and varying perspectives may make age differences a big deal.
I don't think it should as long as the love is there, but then again, I've never dated someone more than seven years older than myself either
True there are cultures that age difference is frowned upon or condoned. I was thinking as well as those countries that have child brides and for them it is not a taboo unlike other countries.