Actually I do own a MTB with slicks for commuting, because it can handle potholes, broken glass, dirt, mud, debris, and curbes; wider tires offers a confortable ride over all those; and an upright position helps looking into traffic. My MTB weights 11kg (24lb), standing better against a similar price roadie. By the way, I have a 23 yo roadie and it's 25mm tires seems unsafe now to me.

Regards