I rode a couple of new bikes here in Taiwan a Montesa 300RR and a TRS 300RR both had teathers and I killed them by forgetting i was attached frankly though I liked having them on because they were not my bikes and knowing that if i made a mistake they shut off. The cost a trials bike in Taiwan is like buying a car. I like this group of riders here.
As for the guys riding there vintage bikes I don't think they should be required to that like making someone who has a 1970 hemi cuda convertible and making them put in airbags these guys have been riding these bikes for years in most cases.
Ive seen the pics and videos of the vintage riders when their bikes were not vintage, heck they didn't even wear helmets and oh there were a whole lot more riders back then.