Now I get it. And I agree.
It also depends a lot on the cultural environment. I grew up in a somewhat secular environment and it was therefore rare for me to find a married couple. So I grew up as if that was the norm. But I do think marriage is taking it a step further.
An unmarried couple can vary greatly in the range of closeness, intimacy and level of commitment. But when a couple is married, a high level of all of these is assumed.
I would say it depends on the couple in question.
So, yes, I agree.