For a lot of simmers, the driver behind their passion is the desire to fly one of those heavy jets. I have a PPL, but unless I committed about a decade for it as a career, there's simply no way I could ever find myself behind the cockpit of an airliner. Simming is the only way. You do see people make cockpits for smaller aircraft, but it is definitely the exception, and usually those people do have licenses and use it for flight training.

Also, you can find airline-quality simulators out there who will gladly rent you some time, but last time I checked the full-motion 777 simulator I had available to me cost $750/hr.

Also, outside of the US, a PPL is pretty damn expensive!