Totally not negative on this but I'm not a Skype user so can someone please explain to me why anyone would want to go to all the effort to reverse engineer it?

Totally not negative on this but I'm not a Skype user so can someone please explain to me why anyone would want to go to all the effort to reverse engineer it? I get that its closed and should be open, I get that its security is in question but if you want a more secure communications platform I can't imagine Skype is the only way forward and must be reverse engineered. Why not contribute to an existing open source project?