Google also does a horrible job in urban areas, giving businesses a dozen miles away (~ 1 hour travel time) over businesses within a five minute walk.
I'd understand it if most of the local businesses that forgo an online presence were all 1-4 person, family operations where they're all too old to have a "Google it first" mindset. However the majority of businesses that refuse to register themselves with Google have no excuse. I can search for the closest laundromat, tire shop, florist, etc directly by name and address and the only results will be those sites that scrape the secretary of state's corporate filings.
Google has made the process of creating an online presence the simplest, most painless process imaginable. Google's My Business service gets you on Maps with all the important info (location, hours, services, etc) for free, yet so few businesses take the importance of being a top, location based result. If a business doesn't come up in my location based search it's as good as if it never existed.
On the anecdotal evidence side there are 3 laundromats within about 2 min walk from my house, 2 are on a high street and can be found in Google, one is a part of a chain but the other is owned by a Persian guy who's way into his 60's (which still owns a flip phone, and i don't think he knows how to register with Google), 1 is in a mews (like an alley for you yanks) and it's not listed, the coffee shop in the same mews isn't listed either even tho every coffee shop on the high street is. If you open streetview you can walk through the high street but you can't get into the mews.