Marriage can be a great thing for lots of people. Many who marry find happiness and success, as two people who love each other can live with each other for rest of their lives, or until death due them part.
However, their are rules that every married couple expects out of each other, and with good reason.
Some folks who are married believe that it's OK to "innocently" flirt with other people of the opposite gender, that is, flirting with no intention of starting a relationship with others.
I'm not a jealous type. But if I get married someday and my spouse starts flirting with others, I would not be a happy person. If I were married, I would never flirt with other women in front of my wife or behind her back.
And I would expect the same from my wife.
To me, "innocent" flirting is unfair and inappropriate for those who are married. I don't see what the purpose of "innocent" flirting with others when your married is anyway.