Why is Phil always reaching his vest goal and not having slow shtreams any more? Because the vest uses several psychological tricks. It's the mcguffin that makes the $100 goal work.
Let's face it, all goal incentives are meaningless because you don't get anything in return for your payment. Whether it's bodypaint on a thot's titties, hearing your name spoken, or seeing an animated popup - they're all meaningless. So the vest is no more bizarre. You get to change Phil's appearance for the rest of the stream. The vest has some psychological tricks that the plain bare $100 goal didn't have: Once the goal is half way it creates a feeling of: "We're half way there, it would be a shame not to reach the vest." Phil was usually able to make $50 even on Slow Shtreams, but now $50 is "half way to the vest."
The vest streak works on the same principles -- the next psychological milestone is 100. "It would be a shame to get so far and not reach 100." It's a bit like the fallacy of sunk costs: "We've gotten Phil to the vest goal 78 times, it would all be for nothing if he doesn't reach 100."
Phil stumbled into the vest accidentally, but he is surely now aware of why the vest works, and aware that his $200+ per day will no longer be guaranteed once the streak ends. This is why I think Phil was an utter scumbag when he failed the streak in the 70s and used pignosis gaslighting to say it doesn't matter: "only mentally ill people would care, I'm not resetting the streak."
The good news is that I don't think the vest streak can continue past 100. The next mental milestone is 200, and that might seem insurmountable. I expect the vest streak to end somewhere around 104 or 105, and then the spell will be broken.
But who knows... the universe seems to be rewarding this eternal cockroach right now. The wheelchairs want to see that vest even more than Phil wants sweaty wrestler jpegs.