It's because he was the first dumbass who recorded himself masturbating in a live stream, that's why he's "The Guy". Phil can cope all he wants about how people have done worse and how him beating off on camera wasn't even explicit, but that's missing the point. The point is he's the first retard that actually did it because he's that fucking stupid. Phil beating off on camera isn't funny because the obvious, it's funny because he had to do it ON CAMERA. Like of all places he had to do it, he chose to do it live and in the one place he shouldn't have. This is why him trying to make fun of Destiny or ProJared didn't work, because those were private videos that got leaked, so regardless of the person or context, in the end those videos were not supposed to be public, whereas Phil beating off on camera was entirely his doing, it wasn't an evil mod turning the camera on or changing scene, nor it was Leanna leaking some private video, no, it was his dumb ass.
It's similar to Pewdiepie and the bridge incident. Of course many have called people nigger in videogames out of anger, it's something people can relate to, but why do it live when you are a known streamer? That's why both May the Burst and The Bridge Moment stand out, they aren't the worst, most heinous things caught on camera, but both were the first notorious cases of people doing that. It doesn't matter if someone like Rich sucks on a cucumber or PPP shows his asshole to the camera, in the end Phil Burnell is the guy who pioneered the "beating off on camera" genre. Anyone who does it will automatically be linked to DSP, and that being his true legacy will always be funny.
And of course, him being incapable of just rolling with the punches is why it becomes even funnier. Pewdiepie has accepted what he did and can even joke about it, but Phil is still making excuses about it.