Why?
For one thing, married men burp;a lot. They make other noises too
Maybe it has to do with my own marriage. If something is troubling me, it will affect my relationship with my wife. I have discovered over the years that keeping my troubles from my wife only invites more trouble into our home.
When I said that I would have trouble confessing my sins, I wasn't necessarily talking about me. Thankfully, I am now in a place where my sins are pedestrian enough to put the most eager confessor to sleep. However, if someone were in an ongoing confessor/confessee relationship, I think it would be difficult for a good confessor to compartmentalize his duties and to keep tough cases from his wife.
I understand a priest has taken a sacred vow, but if he has also taken a vow to his wife, I could picture a scenariao where a marriage could intrude upon the seal of the confessional.