Cindy Williams looked really beautiful in the semi-wedding ep talked about in this thread (post #11). How Carmine could look at those legs and not want to joyfully make Shirley his for all time, I don't know.
I think maybe That Girl had started a mini-trend of TV couples not getting all the way to marriage, but there were lots of exceptions. For example I think Chip & Polly got married on My Three Sons in the fall ('71) after That Girl ended.
On The Mary Tyler Moore Show, Mary had very desirable single men like the characters of Paul Sand and Ted Bessell dating her -- I'm thinking okay, if these guys can't "have" her, she's likely to never marry. (I loved the Paul Sand ep, as the IRS auditor, but it was all just too brief.)
Anyway, back to L & S: If we pair up Shirley & Carmine, Laverne & Lenny, what about poor Squiggy? Maybe Rhonda for him? (lol)