Just as we come closer to ensuring no murders when we enforce laws against murder, we come closer to ensuring the software freedom described in the GPL when we enforce the GPL.
It's telling that Linus Torvalds said "I really think the license has been one of the defining factors in the success of Linux because it enforced that you have to give back, which meant that the fragmentation has never been something that has been viable from a technical standpoint." and hates enforcement ("Lawyers: poisonous to openness..."). The fork of the Linux kernel Torvalds distributes contains the "fragmentation" he claims isn't viable—Torvalds' variant of Linux contains proprietary binaries in it. These blobs of code are removed in the fully-free GNU Linux-libre kernel.
Linus Torvalds' position is more easily understood when you consider that Torvalds is a fan of the right-wing, proprietor-friendly open source movement which is a reaction to the older free software movement. The difference between the two movements has been described in writing (older essay, newer essay) and in every RMS speech for years.
You can see that difference playing out in Linus Torvalds' dig against GPL enforcement. Brad Kuhn, President and Distinguished Technologist of the Software Freedom Conservancy talked about the value of GPL enforcement in his most recent talk on the issue at linux.conf.au in 2016 in his talk "Copyleft For the Next Decade: A Comprehensive Plan", "Copyleft is not magic pixie dust; you don't sprinkle it on some code and then suddenly your code is liberated forever. I wish that were true but that's not how the world works." (9m2s). The way Torvalds talks about the GPLv2 you'd think the GPLv2 were magic pixie dust because that's what he wants Linux kernel copyright holders to believe—an unenforced GPL is fine—because Torvalds, like any good sycophant for proprietary software, knows what Kuhn reminds us of in Kuhn's talk, (around 13m1s), "If a copyleft license is not enforced it's indistinguishable from a non-copylefted license in practice.". But where Torvalds takes that as an instruction to not act in defense of the GPL, Kuhn says that as a warning against software proprietarism. Conservancy is the group doing that enforcement work to help assure all computer users actually get the freedoms of free software the GPL describes. That work includes GPL enforcement, specifically a coordinated compliance effort across multiple Conservancy projects.