Why does my old boyfriend never say his wife's name?

I am happily married to "James", for almost 18 years now. My old boyfriend has been married a long time too. My old boyfriend "Sam", and I have been friends these last few years. Whenever I talk/email to Sam and discuss my husband, I refer to him by his name, James. Sam seldom brings up his wife "Monica", and when he does, he never says her name, just "my wife" to me. I know his wife's name, and have known about her for a very long time. On Sam's facebook, he also refers to her as his wife, never addressing her as "Monica". What does it say about Sam, by never saying/or writing his wife by her name- Monica, and only calling her "my wife". I also have detected that Sam still has feelings for me, but that's besides the point. What I wonder is, is Sam unhappy in his marriage? Does a married person have a troubled marriage, if they can't say their spouse's name to their friends in conversation, emails, and on the internet?