For this simple situation:
What if I want to be freer than the GPL? What if I want to release my next project with a BSD license so that even commercial users or people who want to keep part of their source private can use it?
The GPL is not very suitable for commercial applications. How many fewer people do you think would be using GCC if not for the special exception that allows you to produce GPL-free binaries?
I don't care if someone wants to use my code for commercial software. However, I don't want to give them a competitive advantage just because I wanted them to be more free. I still want to benefit from the changes they've made (if they make sense for me) in the same way they've benefited from my initial work! Now, if I have to pay for a copy of the software to get the changes (since the GPL allows for that sort of thing), so be it. I invited that by releasing my software under such a license.
You can use GPL licensed software and sell it. There is nothing preventing you from commercially exploiting GPL licensed software. In fact there are plenty of companies doing so. You just have to include the source.
You might find this less attractive for your (commercial) goals and needs, but I find it quite attractive and important to have access to the source and the possibility to alter or enhance the software I use, while preventing freeloading (not quite true with GPL, see services as a loophole, AGPL is actually even better at preventing freeloading) to a certain degree.