I have an uber awesome amp, why buy a speaker with a built in woofer sub-woofer amp


I'm wondering why there is a market for awesome speakers that have built in sub woofer amps - e.g. Triton 1,2,3 ; ZuAudio Definition and so many others.

As far as I know built in amps are almost never put under the reviewers microscope. So while the amp and speakers I purchase may well have been, the amp inside the speaker isn't.

So, if I have a really good amp and I'm looking for a good pair of speakers, why would I (anyone) want a set of speakers with a built-in amp, especially one of unknown quality?
128x128jimspov
I concur- not into this kind of speaker either. Additionally, I do not like the sound of speakers that feature side-fire woofers?
Like JOND said, "it allows you to use a lower powered amp to run the mid and high frequencies, typically a tube amp often SET." 

I believe the upper-level Vandersteen's have built-in powered subwoofers.
I've never been a fan of built in powered subs either,  I prefer running my mains full range and using a separate powered sub for below 50 or 60 Hz depending on the speaker.  Every powered sub speaker I've ever heard sounded muddy and colored to me.  
When you say the amp inside the speaker is never put under a reviewer's microscope, that isn't entirely correct. When they are reviewing powered speakers, they are reviewing the amp when they review the amp and speaker as a whole, how the interact together and what sound they make together. It is a review of the amp contained in the speaker when the review reports how it all works together. I think that is the key rather than isolating one part of the speaker over another, it is how it integrates as a whole, whether it was successful or not.
Mike