You’re assuming one thing, that the creator should be allowed to set terms for software they have created. A clothing designer, for instance, has no such rights. Why should software users be restricted in their use of the software by a law giving enormous power to the creator?

That is the essential question you must answer. Arguments against are legion: https://en.wikipedia.org/wiki/Opposition_to_copyright

The GPL license is not an end in itself. It is simply a holding action – a means to carve out a bit of freedom for end users using the current rules of copyright.