Commuting is, as many have already said, different from racing. Two considerations come immediately to my mind. First, you can't count on your road surfaces. An example: yesterday I went out to do some shopping. About a mile of my route was torn up. No marked detour, no obvious alternative (a lake to the north and a limited access highway to the south). Riding over the dirt, gravel and soft sand was lot easier with wider tires. Second, although in general skinny tires are faster, wider, lower pressure tires can actually have less rolling resistance than skinnier higher pressure tires on roads that are less than perfect.