Is it fundamentally different from car insurance? It might not be very useful to them if they get in a fender-bender, but a high deductible plan can still save their bacon if they have a health catastrophe.
If you can barely afford the deductible, you will NOT be able to afford the bill at the end of the day for anything remotely complicated like a surgery. You will still end up with a >$50,000 bill you won't be able to pay, because you'll have to take time off of work to recover. There is nothing protecting someone from being fired from their job unless it was a workplace injury.
Everyone in the working class in the US is a single major medical event away from bankruptcy, insurance or not.
I can't speak to every insurance plan out there but there are typically out-of-pocket maximums and other limits on spending. A surgery does not routinely cost $50,000 out of pocket.
I learned a fun thing about out of pocket maximums - there's a thousand ways around them. You get a surgery, and they decide to use a "3rd party" doctor with this own billing that isn't in-network? You're still holding the bill.
