Why WOULDN'T Sirius and XM Merge?

Wall Street thinks the idea of the two major satellite radio companies merging makes more and more sense every day. With the stocks of both companies dropping some 30% and the combined paying audience of Sirius and XM being well over 10 million, it just makes sense. But it makes more sense for XM, which has sunk like a stone from $34.65 to $11.01. The percentage drop for Sirius is similar, but somehow going from $4.72 to $3.75 doesn't seem so bad.