I believe you're suggesting that I have the choice between a sealed unit that I can't change, which undoubtedly contains proprietary software or information, and an unsealed unit that I can only feed with proprietary software or information in order to make it work, and that I would therefore always choose the former. There is an argument that by discouraging use of the latter kind of hardware, people might indeed be tempted to choose the former, thus demonstrating an "out of sight, out of mind" mentality.
However, this isn't what the referenced project is all about. Aside from concerns about whose proprietary information is floating around in the kernel and whether its owners are comfortable with it being there, such initiatives make people aware of things such as device initialisation which is being initiated by the kernel, and raise the possibility of such processes being changed and improved. Immediately, there's an obvious parallel between these binary blobs and more traditional proprietary software which isn't easily waved away by using words like "firmware".
I concede that hacking the firmware of a hard disk controller, for example, would be a fairly specialised activity, but there might still be people interested in doing so. And the history of Free Software has demonstrated that what might seem like an uncommon area of marginal interest today could be a popular area of customisation tomorrow. The open hardware movement is showing that the choice I appear to have isn't always limited to those two options I mention above.