There is a whole bunch of stuff behind the scenes that you wouldn't be exposed to as a consumer, such as analytics data pipelines, ad sales interfaces, etc that in many ways are more complicated and do more than the consumer facing thing itself.

An old EHR system from years ago does none of those things, doesn't do engineering heavy things like live updates with thousands of A/B/C/D tests running simultaneously with multiple clients for multiple operating systems and so on.