Hybrid SACD is a sort of dual-layer with a CD layer and a SACD layer which is DVD density.

As for the original question: the capacity of DVD was needed for video, for which there is a huge market and therefore reason for investing in development, whereas there was no commercial incentive to develop a two layer CD that would be incompatible with single layer CD players and hot have sufficient extra capacity to be useful.

CD capacity is 650MB (data) and 750MB (audio)
Dual CD would be 1.3GB / 1.5GB
DVD is 4.7GB (basic 12cm single side single layer)