It's a medical device that requires a prescription. You can't buy it off the shelf. They're not distributing software to you either. You must go through a medical equipment supplier who transfers the device to you after insurance has paid for some or all of it.
For the same reason you can't find an airplane entertainment system in the trash and call up the company and demand source code.
For the same reason you can't find an airplane entertainment system in the trash and call up the company and demand source code.