Different people's relationships work in different ways. If I were in a new relationship, or with someone I didn't trust, then I would be more inclined to agree with you. But, to me, a marriage means no secrets at all. There is nothing I would deliberately keep from DH, nor him from me.
I trust that he wouldn't tell anyone something that was a secret, and I trust him to act responsibly with things that I tell him - and the same goes in reverse.
It's not a cop out at all. I couldn't imagine being in a marriage where that wasn't the case.