Only 1 reason for going MFT?

BobT wrote:

Is the one-and-only reason for going into Micro 4/3rds, the lesser size and weight of the gear? Is there really any other reason to go that way? I understand that with inexpensive adapters one can use a large variety of older MF lens on MFT camera bodies. But, if you're really attached to those legacy lenses, can't you also adapt them to your DSLR (non-MFT)gear, too?

I'm not downing this size/weight reason as unimportant. That's why I did it. But is that the ONLY TRUE reason for the gear?