When you purchase a device, it is reasonable to expect that you can continue to use it until it wears out. However, devices that connect to computers require the manufacturer to continually update the software drivers that make if function whenever the operating system is upgraded. Frequently one finds oneself in the position where an expensive device can no longer be used after Apple or Microsoft alter their operating systems.
By requiring that drivers for obsolete products are open-sourced, owners of obsolete products will be able, if they wish, to continue to maintain and upgrade the drivers themselves and thus extend product life to its natural end: when the product wears out.
If trade secrets need protection, then manufacturer can require an NDA signature for source code access.