I think that an important point that you're missing, Janne, is that for we -- non-programmers members of the community -- it is not that easy to avoid (or simply stop) using those blobs, most of all when they are inside the kernel. To be sincere, I have absolutely no idea how many of them I run into when I use computers.
Having the option of a free kernel/distribution that -- just for starters -- lets you know exactly what pieces of hardware you have that would not function without blobs seems, for me, very good indeed. I believe that might help people (esp. non-programmers, such as you and me) wonder about what kinds of trade-offs we're making, how we could proceed differently etc. For example, how do I choose compliant hardware? Or, do I really want high performance 3D acceleration, considering that this would require me to accept many other bugs, eventually tiny but certainly resilient (as they would probably no be fixable by the community, because they're inside blobs)? Does my need for high performance 3D acceleration outweighs the value that I put on using and helping free software?
One of the things that I value in free software is the fact that it helps us in trying to overcome planned obsolescence for hardware. In that sense, choosing free over blob helps the community in making free, good drivers for old hardware -- something that is mostly ignored by hardware companies, which are interested in selling us more of their latest release. That latest release might work right now (with blobs), but of course the companies are not willing to guarantee that it will work when it becomes "old hardware".
The transparency of a completely "just-works" kernel deals away with the pondering of those issues. I believe I'd be much more hardware-conscious, as you suggest (in what I believe is your main argument: free kernels are unnecessary as long as people use free, compliant hardware), if I knew exactly where are the blobs, why they are needed etc. Then, one would even be able to decide that he can't "afford" to use the free kernel, and therefore stick to the nonfree one -- but at least it'd be an informed decision; which in the future could help that same person in avoiding a bad hardware purchase, and therefore in avoiding proprietary software.