Active bi and tri amping is routine in professional recording studios, theaters, and other applications. There are also a good number of active speakers available like the Mackie HR 824 which have built-in power amps and active crossover.

The technical reasons for the superiority of this setup could take pages to list, but basically a passive crossover presents a complex reactive load before the signal ever gets to the speaker drivers. The passive components are wasteful of power and add significant resistance in-line with the woofer. This destroys a great deal of the damping factor of a good power amplifier. I could go on and on, but suffice to say, the benefits are extensive. Also, you can use power amplifiers that suit the particular frquency band to be reproduced such as a smooth tube amp for the highs and a good, stiff solid state amplifier to control the woofer.

The reason you don't see is in the consumer area is because it requires some advanced knowhow in setup to get it right in addidtion to an RTA/calibrated microphone. The required expertise is very rare in the "high end" audiophile dealer networks - the knowledge is routine in the professional area. I have never met someone in a consumer dealership that had any knowledge of active systems, and of course they are in business to sell what they have - conventional speakers with passive crossovers.

The reality is that most audiophiles would be overwhelmed with the setup variables required with multiple amplifiers and crossover setup, let alone the average consumer. However the extra work is well worth the effort, and much more productive than endless futzing with cables and other boutique tweaks. Acive crossovers make real and obvious improvements in the performance and sound of a system.

Another reason that speaker manufacturers especially have not embraced active crossovers is that it takes control of the "sound" of a particular speaker out of the hands of the manufacturer and places that control in the hands of the consumer. In other words, the consumer can make their speaker system sound pretty much how they wish with an active setup - the manufacturer is just supplying the raw drivers and the cabinet in essence. It's easy to see why most speaker manufacturers would not like this idea.