It's amazing how Richard Stallman brings the probably most asked question to the point.
The advantages of free software — GNU Project — Free Software Foundation (FSF): "The advantages of free software
by Richard Stallman
People outside the free software movement frequently ask about the practical advantages of free software. It is a curious question.
Nonfree software is bad because it denies your freedom. Thus, asking about the practical advantages of free software is like asking about the practical advantages of not being handcuffed. Indeed, it has advantages:
* You can wear an ordinary shirt.
* You can get through metal detectors without triggering them.
* You can keep a hand on the steering wheel while you shift gears.
* You can pitch a baseball.
* You can carry a backpack.
We could find more, but do you need these advantages to convince you to reject handcuffs? Probably not, because you understand that your freedom is what's at stake.
Once you realize that that's what's at stake with nonfree software, you won't need to ask what practical advantages free software has."