Liquid fueled is far more expensive to maintain than solid fueled.
Liquid fuel is deployed sparsely, meaning it needs more cost and personnel on communication instead of unmanned solid fuel launch facility. It is cheaper to deploy ICBMs collectively with terminal defense system to ensure survival rate. TLDR, solid fuel is cheaper to maintain.
Also it is still open to debate whether it is a good thing to increase warhead-missile rate. More warheads on a missile means more warheads to be destroyed in a first strike.
Do you agree with 9 dash line that nuclear war is imminent ?