While I think that most questions asked on SO where it would be useful to use math formatting are probably off-topic and more appropriate for CS Stack Exchange, it would still be much easier in many cases just to answer the question on SO than to try and migrate it. I don't see how having the math formatting on SO would conflict with anything else. Some people simply don't know about CS Stack Exchange, and so it is easier to ask a question on SO.
I know I have answered questions on SO where the math notation would have been useful. There are instances where you want to talk about algorithm complexity while working with code in a particular language.
As another note, why the heck can't I get code coloring on CS Stack Exchange? Since CS Stack Exchange is smallish and there is a decent amount of overlap between CS Stack Exchange and SO, I really think we ought to just merge them and support math typesetting in SO.
Basically, BOO to the people that declined to implement this. It shouldn't be hard, since it is already in place on other sites, and it wouldn't really conflict with anything. If I knew more about how the sites worked, I would do it myself.