Why can't a 722 dish network reciever with a dual tuner output HD to either TV?

Answer 1

You are correct, only TV1 can get HD signals vie either HDMi or component. TV2 receives only SD.

TV2 receives its signal from coax, so this poses certain constraints. There is no standard for sending analog HD over coax. If they send a digital signal, then it assumes that TV2 has a digital tuner. If you need to have both TVs receiving HD then you need two HD boxes.
I suppose Dish assumes that at this point most people have a single HD TV at home and it may not be cost-effective to add an HD modulator in the box.