I noticed this same effect a few years ago and I think I know why. Most pro shooters are more concerned with losing highlight detail, knowing that when it’s gone, it’s gone. Pro level cameras tended to place the exposure either right on what a hand held meter would read or a little bit under (meaning, darker).
The average consumer, though, doesn’t tend to worry as much about blown highlights and is more concerned with midtones looking good. So, in several consumer (and even some prosumer) cameras that I have tested, what I see is a one to two stop bias towards overexposure – that opens up the mid and dark tones at the price of losing highlights.
It makes sense, but it’s a little annoying when you have to switch between camera models often. (Currently, I teach on five different DSLR cameras: one is clearly a consumer grade camera, one is a prosumer level body and the other three are pro level pieces.)
How do I deal with it? Every camera I have, from the top of the line down through the point and shoot, is set to shoot in RAW mode. (Actually, RAW plus JPG so I can work the images on my iPad if I need to. Once I download onto my Mac, I toss all the JPGs and just use the RAW files.)