Doktor Avalanche
I think you will find most manufacturers won't release Win10 drivers until it is fully released.
In a way I don't blame them restricting the OS as people would end up asking for support on an OS that even MS doesn't support yet.
The big guys all have Windows 10 drivers out. They want them out for testing, if nothing else. Intel, nVidia, AMD, Realtek, etc all have Windows 10 drivers out and available for download. It tends to be the smaller or more specialty companies that lag in drivers.