It was an extremely, easy-to-use language that even laypeople could write business logic in. Similar to how BASIC got so many people started. Except, Fortune 500 companies were writing all their backend stuff in COBOL on mainframes from the 60's onward. Needless to say, there's a lot of it around dependent on existing libraries, interfaces, language variants, compilers, etc. Porting it is huge risk. So, they just maintain and extend it.

Main vendor even has it on Visual Studio: http://www.microfocus.com/solutions/cobol/index.aspx

The job is boring, predictable, and 9-5-ish at most places. Exactly what some types of people are looking for. They figure they can play with the fun stuff at home. One person even jokingly made a web framework for it: COBOL on Cogs. So, yeah, I throw COBOL at anyone using the "use language X for users or jobs" argument to see how they react to what they're actually arguing.

Interesting that you at least looked it up and didn't go into denial mode. I'm impressed. ;)