I don't think that's entirely accurate. It's true that billing is a core part of most EMRs, but out of the hundreds/thousands of features in a big platform like DrChrono or EPIC, a large portion of them are not billing related.
There's tons of operational utilities like e-prescription, lab ordering, patient problem tracking, vital sign tracking, imaging and diagnostics tooling, etc. You could argue that all of those are somehow related to billing because they help doctors see more patients per day, but billing would still be possible without them, and they largely exist because doctors need them to work effectively and treat patients more efficiently, not because they directly serve the billing pipeline.
Good luck using a piece of paper to e-prescribe a medication such that it's shipped to the patient's pharmacy before the patient even shows up. Ditto for lab orders, imaging analytical tools, custom vital tracking with automatic flagging, diagnostic hardware integration, etc. there is lots of stuff in modern doctors offices that would be significantly more difficult on paper.
Not to mention all the issues of paper management and physical security once you have thousands of patient documents scattered around in filing cabinets.
There's tons of operational utilities like e-prescription, lab ordering, patient problem tracking, vital sign tracking, imaging and diagnostics tooling, etc. You could argue that all of those are somehow related to billing because they help doctors see more patients per day, but billing would still be possible without them, and they largely exist because doctors need them to work effectively and treat patients more efficiently, not because they directly serve the billing pipeline.