If you guys are finished puting each other down, the actual CSPAN3 answer follows:
DBS as a condition of its liscense is required to carry so many "public interest" stations. CSPAN counts, obviously. However, to protect a "diversity of viewpoints" no more than two "public interest" stations can be from the same owners (the FCC was worried that the providers would just find some half-baked ranter and let him have 40 channels to rant on). So CSPAN3 does not count as a public interest channel for DBS, so there is no incentive to carry it.
CSPAN has asked for an exception, but been turned down.
Good post.