Ribbon midrange pros and cons

Ribbon tweeters are fairly common on some high end speakers. ...they sound great.....can anyone tell me why ribbon midranges are hardly ever used by some of the best speaker companies. ..what are the pros and cons? 
May have much to do with production costs and logistics for the mass market. Being an Apogee owner (Duetta Signature and Scintilla models) there is a reason (in earlier post)  why someone drove from Indiana to NY to get them. Yes they can be challenging to set up, yes they are obtrusive to some and yes the Scintilla’s are tough to drive. Once set up correctly they are quite remarkable top to bottom without subs, IMO. And just to strike some balance i do enjoy my old LaScala’s and my buddy’s Golden Ear Triton reference speakers. So many great and unique choices. But they are no Apogee...:). 

With the DSP sub/servo stuff today it will be interesting to hear how the new PS Audio AN’s sound with midrange ribbons. I am sure a great outcome.
Over the years I have owned Acoustats (3 panel model) then switched to ribbons, (Apogee Full Range) kept those for a couple of years, used Krell amplification as a logical choice, after which I upgraded to the Apogee Grand, a speaker way ahead of it's time, and for the few Grands still playing at this very moment, they will still be top contenders. I had to sell mine due to moving house, and the new house not suitable for these rather big speakers. After some years moved to a bigger house again, and currently again using ribbons, well hybrids. (Gryphon Pendragons). I have heard many speakers, but will stick with the hybrid combination. For those who believe that ribbons (Hybrids) can't be enjoyable, feel free to visit, it may change your opinion....
 I’m surprised that nobody mentioned Strathearns that address a lot of the problems mentioned. They are great from around 400 Hz on up.  There is no need for a transformer if you put a couple of resistors in line with the amp.
The old Heil AMT1 speakers had ribbon drivers in a semi-horn bidirectional enclosure that were pretty awesome sounding in the ribbons range, which reached down into the midrange.
A slight correction to Raul's comments.  The  Classé DR 3-VHC is not a 25 watts/ch amp, it is spec'd at 45 watts/ch in pure class A.  The smaller DR 2 and DR 3 were rated at 25 watts/ch.  They could all be bridged and basically quadruple their power while remaining in pure class A.  All 3 amps would be able to drive the Scintillas (and they would deliver full power in class A).

Regarding ribbon midranges, the top model Genesis speakers designed by the late Arnie Nudell used B-G ribbons that shared many similarities to the the ribbon used by Bob Carver in the Amazing Platinum Speakers (I think Carver used Kapton, and B-G used Mylar).  Those ribbons are extremely easy to drive (they are basically a 6 ohm resistive load), and excellent sounding; however, there are no longer produced so they are no longer a feasible option for speaker manufacturers to consider.