Copyleft is a hack of copyright that ensures rights to users of software that you wouldn’t have if there was no copyright. Software is different from other creative works like music and books in that it does computing. Sharing a binary file freely isn’t enough - you need the source code to keep it maintained or change it to your will (through collaborative efforts). You prevent others withholding the source code via that copyrighted license. You can reject the unreasonable sentences of copyright infringement, the illegality of breaking locks on your own hardware, or the long copyright terms while still promoting copyright for copyleft’s sake. Companies lobbies for those laws to prevent "stealing’. throwing people in jail or fining them into oblivion - are they going to undo all that? Can I share Disney films without going to jail now?