Some people define "freedom" with 10 pages of restrictions of which the exact interpretation is continuously debated years after release. Other people consider that the opposite of freedom.
Some wouldn't mind their open-source software integrated into high-frequency trading systems and military munitions, and others either object on moral terms or wish to be paid fairly for such lucrative use.
Do you think programmers shouldn't have the choice to decide whether their software may be used to kill people or cause the next flash crash? GPLv3 allows programmers to share their software while making sure big corporations and defense contractors steer clear.