> none of the suits was filed by individual developer who was contributing to the code base

(You're not implying otherwise, but this seems like a good place to put this comment.)

An individual developer can bring a case against a distributor violating the GPL if they can prove that their code was involved in the violation.

A good example are the contributors who brought a Linux (kernel) case against VMWare:

https://sfconservancy.org/blog/2016/feb/29/vmware-hearing/