It is simple, but not having had experience with source control is usually an indicator that the developer in question probably isn't very good.

And yes, I did basically just say that I'm probably not a very good developer. :)

From a hiring standpoint its not something I look for in recent graduates. I also don't ask whether you have learned to use an IDE. Those just aren't things I expect you to have been taught in a high-quality cs program because those are things I expect to teach you on the job in under a week - along with all the other project specific things you will need to learn (like which frameworks we are using, what coding standards we use, our check-in policy, etc.) If you have learned to use them and are familiar with them, great. It won't really affect your chances of being hired though because in our next project we may be using a completely different set of tools, and I will expect you to learn how to use those instead.

Now if you are claiming 5+ years of professional experience and have never used a source control system that is likely to trigger a whole set of negative questions surrounding what kind of experience you actually have, but it isn't a deal breaker - just a warning sign.