[junon]

I went down this road a few times. Tax laws, contract bidding, and money are the main reasons. Plus, writing such systems requires a large overlap of technology and medicine, which means a lot of high salaries on your payroll. Then you need to find places to buy it. That means getting hospitals and the like to break their usually multi-year contracts with Epic (they are largely subject to Sunken Cost problems as Epic costs a LOT of money).

And so on.