At least in the northern climes, it's the last chance to aerate or plug, overseed, and fertilize if you want a half-decent "grass garden" which is suitable for walking and dog abuse. As I always say, lawn grass is a garden. It's not natural, and needs care just like any garden. Lawns benefit a great deal from fall fertilizing. If lawns are walked on at all, they require aerating. It's not a rug. If you have a small lawn, you can do that by hand with a hand aerator or a spade: stick it in, wiggle it, and pull it out.
A Spring or Fall aeration or plugging, a Fall overseeding, and three fertilizations per year ought to be good enough for any grass lawn, with or without irrigation but using a mulching mower. Readers know that I top-dress in Spring, but it might not be necessary for everybody. I like doing it.
(The only purpose of irrigation is to make a lawn green when it doesn't want to be green. It's fine for ahow, but spray paint might be cheaper.)
I advise doing those chores all at once. Do it now, and if you have a crabgrass problem, you can deal with it in the Spring with crabgrass-preventer. (You can't overseed and use crabgrass-preventer at the same time because the weed-preventer will prevent germination of your grass seed.)
Best, most logical plan? Minimize your lawn and grow lots of trees and shrubs, and mulch the heck out of them. It's a shame that the "gracious lawn" became the American Way, as if our little 1-2-acre plots were English estates. Heck, all anybody needs is room for Croquet and Badminton, some walking paths and maybe a cool little putting green, but the American lawn has become the expected standard.
