As a female, how will you feel to have relationship with a married man?In several countries such dating is punishable by death.
Traditionally marriage has meant that a couple are faithful to each other, both in deed and spirit. That means not dating others in the sense of a date being the lead up to a deeper relationship with sex etc. Such relationships are frowned upon in most cultures once a person has entered the state of marriage.
Sure there are "open" marriages where both partners may have sex outside of the marriage and so on but they are the exception rather than the norm.
In my case I would never cheat on my wife and she wouldn't cheat on me, it's just the way we are. We both took our wedding vows seriously with a hybrid set of vows between Chinese and English wedding vows.