FBN launched with just south of 30 million households. In comparison, FNC can be seen in 85 million households, CNN in 88 million households, and ESPN in 100 million households. FBN is small nuts compared to the big boys and there really is no excuse FBN couldn't have launched to at least 60-75 million if the launch carriage contracts were done right (both in getting contracts signed early and in the contract terms of initial carriage).
The only way you can watch FBN where I live is on DIRECTV (not on cable, not on DISH) so obviously not a very large number of households at launch.