Aside from the knobbies, how is a mountain bike any less suitable than a true road bike for commuting?

Cons of mountain bike:
- Knobbie tires
- Suspension fork adds extra 2-3 lbs

Cons of road bike:
- No rack or fender eyelets
- Caliper brakes limit you to 25 maybe 28 mm tires
- Even if you manage to get a rack on it, it has short chainstays
- Many road bikes don't have anything close to a gear setting that's even close to a 1:1 ratio, makes carrying any load up hills difficult without getting out of the seat

I dunno, I think the problems with a mountain bike are overlook-able or easily fixable in the future. I dunno if I would say the same thing about a road bike. I am pretty much never going to buy a bike with caliper brakes simply because I refuse to be limited to 25 or 28 mm tires and there aren't any cheap ways to change out of calipers. It's quite a tragedy that so many bikes are closed off to me as well as their potential utility for simply lack of eyelets and brake bosses; it's not like they weigh that much.

Besides, if exercise is one of the reasons to commute, then what does it matter if it takes a little longer to get there?