It does make it harder to make money from your work, and it's the closest you can get to that while still using a (well-known) open source license. I have no doubt that lots of people are indeed using the GPL for that purpose; look at pretty much any GPL-vs-BSD debate for further proof.
That said, yes, the GPL doesn't actually make it impossible to turn a profit.
Not really. MySQL was multi-licensed and MySQL AB, Sun and now Oracle can re-license it under any license their clients want, provided they pay the price.
MySQL AB was sold for about a billion dollars, proving you can make a whole lot of money while still writing software that can be obtained through a license that respect the rights of the users.
That said, yes, the GPL doesn't actually make it impossible to turn a profit.