Drivers in kernel kernel drivers

Why dosent Nividea put the drivers in the Linux kernel, its free and will make life a lot more easy for users.
Can be done [url=“An Interview With Linus Torvalds: Linux and Git - Part 1 | Tag1 Consulting”]An Interview With Linus Torvalds: Linux and Git - Part 1 | Tag1 Consulting here External Image

Because NVIDIA regard their driver software to be a trade secret.