I don't normally pay attention to the back of the bus C- seat chart because I normally get an "instant upgrade" to C+ immediately after picking a middle seat in the back. I assume the OP's experience is the common airline practice of blocking most of the coach seats to scare people into needlessly buying up.

In general, airline travel is unbearable unless one has at least some status or decides to just pay for first class. If OP lives in Seattle, it should be pretty easy to get status on Delta.