Look at all this lovely public domain code:
http://www.blitzbasic.com/codearcs/codearcs.php
Loads of people must have used bits of code from these archives in their commercial/shareware/portal-sold games. If this stuff was under the GPL, you'd have to make the source code for your whole project available to anyone who wanted it. Good luck selling a game that way!
(The GPL has its place of course.)
http://www.blitzbasic.com/codearcs/codearcs.php
Loads of people must have used bits of code from these archives in their commercial/shareware/portal-sold games. If this stuff was under the GPL, you'd have to make the source code for your whole project available to anyone who wanted it. Good luck selling a game that way!
(The GPL has its place of course.)