You pay five grand for suspension and disc brakes specifically so you can ride down things that'll wreck them.
Fun fact: The sport started in 1970s Marin County with riders racing modified beach cruisers down Mount Tamalpais.
Three billion people watch it and the main rule is pretty much just don't use your hands.
Fun fact: "The highest-scoring professional match ended 149-0, with every goal deliberately scored as an own goal in protest."