The point of the GPL is to bind to the cancerous cells of copyright and neutralize them.
My understanding of the position taken by GPL authors is that the current implementation of copyright in the US favors publishers heavily to the detriment of users [1], that this is unjust [2], and that users deserve certain freedoms [3]. It's not about restricting developers, it's about removing restrictions that shouldn't have been imposed on users in the first place. If public domain is one end of the spectrum, see [4] for the other end.
EDIT: formatting
[1] https://www.gnu.org/philosophy/free-sw.html
[2] https://www.gnu.org/philosophy/free-software-even-more-impor...
[3] https://www.gnu.org/philosophy/misinterpreting-copyright.htm...