That's not true at all. If you call 911 (or someone calls for you), and you don't want to go to the hospital, you have to sign a form saying we offered to take you, but you are choosing not to go.
As rdl pointed out, the liability is just too high to refuse to take someone to the hospital.
When I lived in the UK, I called for an ambulance. The responder listened to my situation and told me I didn't sound high enough risk, so I got a taxi. I didn't get the sense this was unusual.
However, it wouldn't surprise me if the liability issues were very different in the UK.
Even in silly Poland (not to speak of Netherlands) abuse of ambulance service is treated very seriously. If the hospital makes the case that you made a call either as a prank or frivolously, you're in a world of trouble.
The argument isn't that they shouldn't get care, or even that they should have to pay for transport, but that they should be guided (using cost incentives, in the US market model) to use the most appropriate transport. ALS, BLS, mobility-but-not-EMS, or taxi). The problem is there are a lot of places in the US where "take an old person to see a doctor for a checkup" requires using BLS or even ALS ambulances, which is crazy, because ambulance would be covered but taxi would not be. It's better to just give these patients taxi vouchers, if you want the government paying for it, for $10-20, vs. a $100-500 direct-cost ambulance ride.
There's a separate argument about who should pay for what services, but "care should be delivered in the most cost-effective way to get the best patient outcomes" is independent of that.
As rdl pointed out, the liability is just too high to refuse to take someone to the hospital.