Two reasons: 1. If nobody uses your free software because it doesn't interoperate with what other people use, then you're really not accomplishing much by maki

Two reasons: 1. If nobody uses your free software because it doesn't interoperate with what other people use, then you're really not accomplishing much by making your software free. 2. If you want to empower users, you can't very well tell them that they aren't allowed to use certain kinds of software just because you don't want them to. That would be quite hypocritical.