Obviously this relationship expert needs to get out more.
I'll say the reason I am not married and never will be is because I just can't stand being around people for any length of time.
LOL! Seriously, part of the issue is that the longer you're single, the more set in your ways you become, and the less likely you are to change your ways to accommodate a new lifestyle.
My wife and I married (only marriage for both) in our mid-late thirties. By then, we both had careers, had our own things, and we were both used to doing what we wanted without needing anyone else's buy-in or blessing.
After we tied the knot, I didn't think we'd make it a year. That first six months was misery. Then, we gradually knocked the rough edges off each other, laid down some groundrules as to how we'd live our lives, and worked things out. It wasn't easy, but we survived it.
I love my wife, and I know she loves me. But we both agree on one thing: If anything should ever happen to one of us, the other would NEVER consider marrying again.
Then you are kind not to involve someone else. Bravo to you.