Why no fast (<F2) lenses available for 4/3 or m4/3?

Just browsing Amazon and couldn't help noticing that, with the exception of the pseudo-Leica 25mms that Panasonic puts out, there are zero lenses available from Olympus or Panasonic that are faster than F2 and those are Olympus SHG monsters with prices to match. Is this a phenomenon of the 4/3 design? Does the size of the sensors preclude using them with a 1.4 speed lens? I would think, since the 4/3 sensors are known to have dubious low light capabilities, the manufacturers would try to offer some high speed lenses to offset that somewhat.
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MRD