AgentLozen :
There must be some Windows 10 exclusive feature that it leverages that reduces older Windows compatibility.
There doesn't have to be any particular technical reason relating to Windows and it may come with no malicious intent of the developer. It could just be a redirection of development resources needed to both code for and QA test the Oculus Home software for multiple versions of Windows, which at some point happens with all products.
You could even ask if companies that made hardware devices that ran under Windows 98, where those hardware devices are still otherwise in good working order today, should produce drivers to use those same devices on Windows 10. Part of the cost of any hardware device is the software development. The cost is initially covered through device sales. At some point, the end user will either need to fund further support of software themselves (not really a practical option) or accept that the device is no longer supported in some fashion, although it more than likely retains it's original functionality. So, Oculus isn't taking away anything that it's users enjoyed on either Windows 7 or 8 platforms, just offering a better experience going forward on the Windows 10 platform.
AgentLozen :
I suspect that there's a business relationship between Microsoft and Oculus VR (Facebook). The Oculus Rift originally came packaged with an XBox One controller and the Oculus Rift Core 2.0 has Windows 10 specific features. It's not unthinkable that Microsoft "encouraged" Oculus VR to develop in that direction.
Microsoft did have a partnership with Oculus to provide both the XBox One controller and wireless adapter that shipped in the early Rift bundles. I wouldn't however conclude from this that Oculus is obliged to reciprocate by urging users to upgrade to Windows 10. Initially, Windows 10 was a requirement for Microsoft's wireless XBox adapter, which of course has nothing to do with Oculus.
Despite Oculus having a partnership with Microsoft, in 2015 they released this statement:
Our software team is working as quickly as possible to complete Windows 10 compatibility with our SDK and the Oculus Runtime. As Windows 10 is not officially supported at this time, we strongly suggest that Oculus Rift Development Kit 2 owners do not upgrade from previous versions of Windows until we have the officially updated SDK and Oculus Runtime available.
Something else we aren't fully aware of is, the percentage of Rift users who are on each Windows version. If Oculus collects any metrics here, they probably realize already the impact this is going to have on their install base.