Ed Kyle wrote:

Boeing shelved Delta IV Light during the late
1990s after determining that it was more cost
effective to keep flying Delta II. As long as
Delta II is more cost effective, there won't be
a Delta IV Light.

I always thought the combination in the Delta IV Light of a H2/O2
first stage and a storable second stage to be rather perverse in
any case. Sort of like using 4th gear in the parking lot and 1st
gear on the highway.

Jim Davis