If your impression is based on just what you can see driving by at 50 mph on Scott Boulevard (or on Roswell Road, in the case of Sandy Springs) then you don't know WTF you're talking about.
My grandmother lived in Sandy Springs off Johnson's Ferry near Roswell Road my whole life, and I grew up of Roswell Rd near the 120 loop. I know exactly what I'm talking about. Like I said, in Sandy Springs you have older, nicer homes surrounded by horrible run down apartment complexes. Head towards perimeter and Buckhead and yeah, you have mansions. People live in places like Woodstock precisely because they can afford $.5 million homes but want something bigger than a ranch or bungalow. Why pay half a million dollars for an 1800 sq foot 30 year old house when you can buy a brand new 3500sq ft house for the same price? You wold fit in real good with one of my sister's friends who is spending $1400 a month for an 800 sq ft apartment in Brookhaven (just so she can say she lives in Brookhaven) while I pay $1300 a month to rent a 1700 sq ft house out in Woodstock.
Now, I know Google is doing it on a neighborhood basis, so I doubt that most places in these cities won't get it as there are probably not enough people that can afford the $300 up front investment to make a whole neighborhood viable, so it will still be only the rich ones that get this. It just seems to me that picking areas where the income distribution isn't so large would open them up to more customers. Plus it would be much easier to add in fiber to new neighborhoods under construction than existing, older locations; they should have just partnered up with builders and promoted Google fiber already installed in the neighborhood and probably added $5k easy to the house prices.