Why are American doctors so interested in treating their patients?

Hi everyone. I was born and raised in South Asia, and the doctors go out of their way to treat you, they'll try everything they can to treat your condition. The incentive and the motivation is the pay as you system. You're paying directly to the doctor or the clinic/hospital for all treatments and diagnostics. There's no such thing as waiting time or queues. You're consulted and treated straightaway. I moved to the moved a few years ago and the public heath care, has a very strong hold here and in a decade I've never been treated for anything here it's always a never ending queue. What amazes is why North American doctors are so interested in treating people even though it's not pay as you like South Asia or public sector like UK?