A lot of things can go wrong. A company can take the free code, change it slightly to work only with a proprietary file type and then use their resources to promote their version and make their proprietary filetype and proprietary program the industry standard. Unfortunately this sounds too familiar. There are even cases that the filetype is an open standard but obfuscated to make it impossible for anyone (including the original FOSS) to open/save it.

It's pretty much undeniable that the GPL has been a massive driving force behind companies giving back to projects, and it's similarly undeniable that MIT-licensed projects have fewer comparable contributions.

Sure, the community can stay on the open version, but it will still be companies mostly taking without giving back.

Iirc GPL is how we have OpenWRT. Because a company used Linux in their routers, but forgot to release the code initially until sued by FSF or whomever.

Imagine, for example, that your phone has forks of Linux utilities with mysterious closed-source functionality added here and there. And you'd need to reverse-engineer that functionality to have LineageOS and such, instead of just taking the source-code.

Proprietary apps are prone to enshittification, and permissive licenses allow vendors to build their proprietary software on open-source software without giving anything in return.