Compact superzoom cameras, for obvious optical reasons, have stuck remarkably constantly at the 1/2.3" sensor size. CCD has been superceded by BSI CMOS but light gathering did not change all that much. Pixel counts have gone from 5MP to about 16MP, a factor of about 3 in area. A 2005 vintage DSC-H1 offered an ISO64 setting for best quality. Assuming a similar light yield of the sensor, that would imply that similar quality for a modern camera would require using an ISO25 setting. Yet the lowest that is available on, say, a Panasonic FZ200 (admittedly only 12MP), is ISO100. Reviews point out that you basically have to choose between visible noise, noise reduction artifacts, or both.
Now except for indoor shooting without flash or bad weather conditions, light tends to be reasonably available (and actually, a good external flash can do a lot about near objects in bad weather, and a tripod can do a lot about faraway objects as long as they are basically stationary). But no low ISO settings to use the camera in a manner minimizing noise.
Is there a limit to the charge the detectors can hold before bleeding to adjacent pixels or stopping to absorb photons? Or can the A/D converters not deal with it for some reason?
Or is the removal of low ISO options just a victory of marketing over physics? Because it looks good to offer high ISO settings and bad to offer low ones?