They used to do that, using the loophole that drivers technically get 100% of the tip because they were subtracting the base pay if the tip covered it. They stopped doing that but now they don’t show the full pay to the driver to discourage ignoring low tip orders, screwing over the good tippers who tipped well for fast service. It doesn’t matter if you tip well anymore because they’re going to bundle your order with low tip orders and force you to wait an hour to get delivery that used to take 20 minutes. It’s why I stopped using door dash.

It’s because the trapped gas puts pressure on nerves that radiate to the shoulder.

https://en.m.wikipedia.org/wiki/Embrace,_extend,_and_extinguish