Actually most of the LOB applications ditched Win32. They look the same as Win32, but, they are C# .Net Apps in WinForm. On top of that, several years ago when I hunt around the sales-inventory solutions, aside from them all being .Net, some of them are fancy WPF and nice looking charts. Win32 in LOB has been long replaced by .Net and large percentage replaced by WPF.
But, the reason is simple, going to .NET and WPF has zero risk to customer and product provider. Customer can use .NET 1 2 3, without any unexpected behavior and it runs on "XP!!!!!!".
But, metor, modern, UA, UWPA are literally tard. And death of modern Skype proves that. Honestly I started this thread just thinking how stupid of MS to jump ship from their own modern platform. And now I got slapped with some insane truth about why modern platform remains as a joke. The joke is how volatile the platform truly is.
WPF is proprietary, it has the same risks as the others you mentioned. Microsoft can simply kill it, or start charging $50,000 to use it, or whatever suits their current or future business goals (which does not always align with yours) and there is ZERO you can do about it. Thus making WPF a hard dependency of your software is extremely risky. Much of .NET these days however does not have this risk, but WPF does.
I wouldn't even call it risky: the idea of building your intellectual property ontop of some other companies IP that you have zero leverage over is in all circumstances, asking for trouble in the future. It's not about a calculated risk, it's just stupid. It means you have little actual control over your own IP. Your control over your own technology is only as strong as your control over its dependencies.
Some people are always doubters about this, but I get proven right time and time and time and time again. It's not that I have a crystal ball. It's just that I understand that a company is not a charity. They are only interested in your business as far as it suits their own. Once it's no longer necessary or possible to sell a proprietary platform, the vendor's interests will no longer align with your own - they have no need for that anymore.