It is because the insurers and interests [provider groups] represneting the providers want it to be a convoluted mess.

a. No. Some of it is handled by different apps now including Healow, MyChart, etc.

b. The negotiated rates change depending upon what insurance you have. It is coked-up monkey with a random number generator that is making the actual billed prices.

c. Yes. Hippa, the ACA to some extent, different state political interests too.

TLDR -- Healthcare is a hot mess in the USA for all but the very wealthy.