Why are hi-end active monitors not more popular?

I remember hearing a Phillips active speaker 30 years ago and thinking how much easier it would be to have such a speaker. It sounded quite good also. But now they are largely invisible. Other than those on my computer, I cannot remember hearing any in the last 30 years.

Samuel33, I define an active speaker system as one that uses active line level
crossover circuitry to feed power amplifiers which are then directly connected
to the drivers.

I had a pair of ATC active 150's (half again the volume of the large 100's). they were spectacular, but I bought them used unheard, unseen, and they were too large for my room (and my room ain't small....15.25 x 23 x 10). My room doubles as a HD-based 110" home theater, and the sheer size of the 150's was too much for the scale of the room.

ATC active speakers are absolutely audiophile-grade transducers. Their midrange is legendary and they produce microdetail, harmonics and imaging that are out of this world. If I hadn't found great passive speakers in the meantime I would have gone with ATC SCM100ASL's for my mains (and Active 50's for surrounds). One problem: finding large ATC actives used is a pain, but new they are huge$$, even taking into account they cover both amp and speaker budget. The advantages of actives have been discussed here, but are clearly the near-perfect amp-driver integration, the dedicated crossover-amp synergy, and the convenience factors afforded by lack of speaker cables, etc. The results are quite evident; the linearity and "wholeness" of sound is astounding.

I HIGHLY recommend anyone searching for active speakers to go listen to ATC's big boys, the 50's on up. You will have an opinion, no doubt.

Just a general comment. I can see the advantages of a speaker being designed with a particular amp in mind. However, I fail to see any advantage of housing them in the same cabinet.

So the case to be made is not for the amp and the speakers to come glued together, :-) but for the manufacturers to offer matching sets. In a way, that's what Quad has been doing for a long time.