If that's where they have space, that's where they have space. It's a CONUS slot, so, I doubt that will be a major limiting factor. It may be why they don't have national channels there but for example Dish Network has/had core channels there so it's not an insurmountable issue.
DirecTV will surely have less customers if the use the 119 for "main" channels
There's a reason why Dish launched an Eastern arc. It has nothing to do with what the beam covers, it's the elevation of the satellite in the sky.
119 is CONUS only if you live in an area that has no trees, hills, or tall buildings and it never rains. Before the LNB3 came out, I could not get HD through a DirecTV installer because I could not get a signal at all on 119 and the signal was below 80 on 110. I did get an independant contractor to install HD for me, but he was not supposed to have done so. At the time, the only HD channel that I cared about that was on 119 or 110 was ESPNU, and that was moved to 103 or 99 eventually. When the LNB3 came out, I swapped the LNB, because I was tired of getting the guide data not updated error message.
DirecTV would lose most of their East Coast customers if the main channels were on 119 or 110.