Black Waltz's comment makes no sense -- at least not without some supporting argument. We all know that the tesselation of hexes is somehow "nicer" than that of squares, but I'm sure Sid thought of that when he was designing Civ I. He seems like the kind of fellow familiar with games.
The most important difference is in your city radius. Realize that if you had a hexmap, a city would pretty much have to have either 6 hexes or 18 hexes in its city radius. This would obviously have some very deep ramifications for basic city management.
To me, there's no clear way to scale the mechanics of the game by a factor of 18/12 and leave it playing the way it does right now -- growth rate, value of having 1 city versus 2, city density, city production, effects of population limits, etc. And because hexes tesselate so "nicely" it wouldn't make sense to just clip off the coreners of a city's radius -- which corners get clipped? What _is_ a corner in that sense? The problem is compounded with the new cultural system, where your low-culture cities now start with 6 workable tiles instead of 8.
Or maybe it was just easier to program squares than hexes back for Civ1, and he decided to just not change it. Either way.
