why did the one pilot not have an ejection seat?

That model B-52 had 6 ejection seats, one for each primary crew member.  We had one extra pilot sitting in the jump seat between the two pilots, and one spare  navigator, along for the ride as he needed the flying time.

Of the 6 ejection seats 2 malfunctioned.  The crew compartment was tumbling and we were mostly upside down.  So the IP seat has a short step to get out, even though he did not realize it.  The spare navigator had a few long steps to try to climb out a lower hatch that was pointing at the sky.  Maddox I called Rose after that as he came out of that smelling like a rose. 
When his commitment was up he got out to teach school.  Probably missed a few other opportunities to die young. 
OBTW my wife never indicated she wanted me to quit flying.  The Navigator did quit flying.  The Co Pilot kept flying, as did I.  His reward was to be allowed to go to Viet Nam flying something low and slow. From there he was assigned to a pilot training base to teach flying.  The Pilot was given a young junior crew initially and then moved to a more senior crew, before going to staff. 
Two years later I was in B-52 E model at Roswell AFB. The Co Pilot was sent there a year after the accident. From there I got to my favorite the even older B-52 D model.  Loved that plane. It was in a D Model in about 74 that the crew I was on then won the B-52 Bomb Competition.  Shocked everyone as it had an older radar and bombing computer.  The older models had a set of obsolete optics and they refined our aiming enough to beat out the G's and H's   

As I said, I had a good career.