Petitions in Europe are required to be discussed when they reach a certain threshold. The platform does not matter.

even if they do nothing about the petition, it still directly shows that people care about the issue. Its just one of the things that ever so slightly could tip the scales in right direction. But yes, if people think that its all done and good by signing the petition and nobody doing anything else, you might as well yell in the wind about it. But there could be people with a bit more influence that want to do this too. Even the surveys dont get information from every single person of the populace so having many signs could help even if they dont have to immidiately put it on effect.