Some years ago, I was working on a software company that used some copyrighted JAR dependencies that they had bought from a medium-size obscure private company for a very expensive price.
After some time using their JARs, I figured out that most of the content was a GPL'd software that they repackaged, obfuscated, encrypted and started to sell as if they made it.
This is clearly a violation of the GPL terms (don't remember if it was GPL v2 or v3, but it is still a violation regardless of that). However, no one seems to care and I never heard about some lawyer suing somebody who is not a giant global player like Microsoft or Google due to GPL violation.
Further, how would I prove that there was a GPL violation, since the software was obfuscated, encrypted and can't be legally acquired easily? Further, who should/could sue them and how? Since I can't answer those positively, I might sadly conclude that GPL restrictions can't be enforced in practice and thus are just empty words.
I know that this question deeply depends on the country and regional laws, but I expect that answers might give some light about what may happen in practice in most place of the world about this.