Why are hi-end active monitors not more popular?

Because it isn't about sound or value for money; it's a hobby, so people want to believe that they have arranged for a sublime combination. Audio is an ends/means reversal of epic order.

Active speakers are a one size fits all option but this hobby doesnt work like that. Also some sound like Pro speakers and many dont like that.
An active speakers is really just a speaker with an amp built in, when my VMPS speakers are hooked up to amps they are active too.

What about vibration between amp and speaker? It's a little hard to keep the vibration out of the amp when it's in the speaker cabinet. Then you have to run power cables to the speakers. maybe not as much an issues if you are already using mono blocks next to your speakers.

I think there intended use in inexpensive home studio's in the near-field where you will not be listening to them an any level that will severely interfere with the amp.

Powered sub woofers have gained some acceptance so we will see what powered speakers does in the future.

I have no interest in them, if that's of any use to you.

Good question.

Pros:
better driver integration with active phase control
more efficient (no power loss in a crossover)
lower IMD distortion

Cons:
less tweakable
less gear to covet
less resale market

Maybe there are some problems with electronics interfering with the speakers in the active path?

Or maybe manufactures who are good to make amplifiers aren't so good to make speakers and the contrary?