Not to undermine what they did in any way but one thing the Mexica had that favored a strong grid with central planning was that each new bit of the city was bu

Not to undermine what they did in any way but one thing the Mexica had that favored a strong grid with central planning was that each new bit of the city was built on land that had to be created from scratch. If you're going to build a new "neighborhood" from the lake, might as well make it rectangular. To some extent, they didn't even have to dig their canals, just leave bits of the lake not filled in (though there is more to making canals than just digging a ditch). Having said all that it certainly seems that ancient Meso-American city builders of all stripes were really into grid-tastic cities, at least for the monumental cores with the temples, ball courts etc.