Metal cabinet speakers

I think a lot of companies have dabbled in metal cabinets but most don't stick with it.  Infinity did it with the intermezzo line and the Prelude MTS.  Thiel had a number of models - powerpoint 1.2, viewpoint.  ATC had a metal line for a while.  B&W had some metal boxes.  My Thiel 3.7s have aluminum baffles and an aluminum top.  

Do you think they move away just because of how pricey it is and how hard it is to manufacturer vs MDF ?

Genelec still does aluminium speakers. ATC did aluminium speakers for many years. Aluminium works well but I believe it is more expensive than mdf and 3 to 4 times heavier. Impractical for anything bigger than a two way monitor due to weight.

Advantageous material for cooling of heat sinks, good damping, naturally corrosion resistant and non magnetic. My six channel amp is extruded and billet aluminium and is extremely heavy (about 50 Kg) but would be even heavier if cased in thick steel!

I'd guess it doesn't provide enough performance improvement to justify the cost.  There are probably other areas where the money spent on metal cabinets can provide more performance.  The companies that moved away from it are capable of doing a lot of different things, have tried various materials, manufacturing techniques.  I'd guess it's more of a sales feature in cases where companies are making entire big square boxes out of aluminum.  Something to talk about that differentiates them from other brands.  

jon is right. Look what Magico has to do to quiet things down. These guys must love to do CNC machining. That would be the only reason to make speakers that way, YG also. Great speakers if you can afford them.
Wilson's solution of using composites to make individual small enclosures is a good one. MDF is just as good you just have to increase wall thickness and keep the enclosures small with rounded edges and flush mount drivers. Finding great drivers is easy the problems come in designing the crossover.