There is exactly zero reason for an app whose only purpose is to be shown on a screen to be Windows or x86 specific. It can be due to obsolete development practices or obscure vendor requirements, but still..

The main reason is that hiring a bunch of new developers will be 100x more expensive than spending a little extra on a Windows/x86 machine.

Sure the are...

1. LoB apps need to be run not just on a computer that only shows a screen, but in other contexts, there is no reason to develop a whole new app just for that purpose.

2. Developers who are only used to working with Win API's like WPF, DotNet, etc. or other frameworks that are windows only Why would we want to employ whole new dev team just to maintain that app separate from the apps that run on our Laptops and normal computers

3. Management Tools. If my entire fleet of computers is managed by ConfigMgr and controlled by Group Policy and Compliance Setting why would I want to spin up a completely separate management system like Ansible or something just to control these machines when I could have them integrated into my existing tool set of which my helpdesk and everyone else is trained to use?

I can probably come up with 5 or 10 more reasons