Because DDGs are too damn expensive. They’re over twice what the FFG was supposed to cost. But you get less than half the VLS cells so…maybe? But capability wise…no, DDGs are just far more capable across the board. They also need about 50% more crew than a FFG.
In a purely CSG centric battle, DDG makes more sense. You want the best shooters, with the best sensors and networks, with the most VLS cells as missiles are flying around everywhere and everything and everybody really wants to fucking kill the carrier and everybody on it.
As you get to more distributed naval operations, and also operations below the level of a shooting war (eg presence ops) the FFG starts to make sense when needing more hulls also really matters.
Was the FFG62 design the right level of capability and bang for the buck? No idea. But an all DDG Fleet stirs up something like the old F15/F16 hi/lo mix argument.