What does it mean when you ask someone a personal question and they avoid the topic?

This happens to me often with guy friends. I will ask them how their "wife or girlfriend is doing" and they just avoid the question all together. It is seriously a conversation killer but it drives me nuts because why wouldn't you be like "Things are great" or better yet "We got a divorce." My ex thought I was out of the dark for two years but I knew he had gotten divorced. I probed "how's so and so" maybe thinking he'd say something but either he avoided it or said "She's great!" I really don't care about him but I noticed a lot of guys do this. I don't get it. What is the big deal? Is it a guy thing or should I take it personally?