it's all context, no?
You wouldn't try to trick over a 17ft drop on a longboard, either. [0]
[0]: https://www.vice.com/en/article/kzn58e/the-leap-of-faith-was...
Bombing a hill is very different from skating a stair set. The speed at which you do tricks is manageable to be able to tumble your body correctly if you fall (and you’re ready for that fall usually) but bombing a hill is an enormous amount of speed and you can’t prepare yourself for an unknown rock that throws you off.
That’s another somewhat important difference too with street skating, for big tricks you triple check the area and often sweep it because of those tiny rocks.
So context does matter. I’m not advocating against helmets but these are incredibly different things.
Edit: and fwiw I’ve hurt myself far more bombing hills than I have skating something like the big four in ATL. Notice how they fall: https://youtu.be/Ban0D24Aip4
(And the reason they aren’t making this trick is ironically they are not going quite fast enough)
Edit 2: and because I’m reminiscing a bit, the big four is hard because the run up is pretty short. You need good bearings and small wheels to gather the speed required. The only time I’ve ever seriously hurt myself in 15+ years of skating was doing a dumb trick in a standing position. Helmets are important for things like vert for sure where it’s lots of speed and lots of height, and if my kids and I go out and skate we wear helmets (they’re small and I want to set a good example). But most of street skating can be treated as though you’re a trained stuntman (because you basically are)
The 17ft drop is equivalent to the 80mph example in my post, and should definitely involve a helmet, gloves and impact padding (which can be worn under clothes).