It's to prevent people from getting help if they don't have a legit copy of SR4. Most of the time pirated copies have bugs in them that legit versions don't and so trying to work out why it isn't working would be annoying.Why?
Plus, ya'know. Priacy is bad and hurts the developer's chances of continuing work on projects such as these. If accounting doesn't see high enough numbers then management will likely nix projects like SR4 and move on to pandering to the audiences least likely to pirate.
Edit: Also, sorry for my previous posting wherein I insinuate that you are a pirate.