I'd rephrase parent's statement to "that reason is an attempt to maximize the relative amount of software that is free."

So, if with BSD/MIT you'd end up with a few more contributions, but you'd also help a few companies build proprietary software that restricts their users, it's better to use GPL since fewer users end up being restricted by proprietary software.

And yes, I know that the users have the choice to not use proprietary software, but regardless of that discussion, that still doesn't mean you should help that happen.