As to why there aren’t more active speakers available, I think it’s due to the flexibility of picking your own amp at your comfortable price point and also being able to upgrade in the future. So you have both flexibility of sound characteristics as well as being able to spend less upfront with the option to improve your system later as funds allow. But that’s just my guess.
A pretty good guess and something Andrew Jones pointed out yesterday in his presentation to the San Francisco Audio Society. He admitted the amplifiers in his active speaker design takes away consumer flexibility, but he also talked about the benefits from a design perspective, especially removing the crossovers you that do nothing but color the sound with their "EQ". The presentation also included a demonstration of two ELAC Navis active designs, a book shelf and floor stander, neither use DSP in the design. Both were quite good and are priced very reasonably at approximately $2500 and $4500 respectively per pair.