Today, all of those same stores are available except for the dairy (regional consolidation) and we've gained a handful of doctors and even specialist, but they've all grown and carry a wider variety of goods because, within 15 miles, there are another 3 small grocery stores, 2 major supermarket chains, a Walmart, at least a dozen clothing/shoe stores, 3 more lumber/hardware stores, at least a dozen autopart stores, 4 appliance vendors, and regional stores that no particular town can support on its own (say, a farm equipment dealership)... and within 30 miles, there are hundreds of competing stores, some selling stuff that we simply can't get locally.
The car allows non-urban people to access a vasty wider variety of goods at different levels of quality and/or price points that weren't available before cheap travel. Sure, we're spending more money out of town, but it means I can actually buy a keyboard the day I need it, that I can find the part I need to fix my faucet or that I can easily get clothes that don't come printed with the name of my town on it (and something more than a basic tshirt, sweat shirt or pair of jeans at that). If you think every small town can support every store selling some niche product line, you're very wrong, which is part of why mail order was so popular in the early 20th century when travel was harder. And much like our horse-drawn ancestors, I consolidate my shopping trips when I "travel to town," meaning I might go to the doctor, buy food, and stop at the hardware store all in one trip. It's not like I have to drive 30 miles for every store I need to stop at in a given month, especially if I do a little planning ahead of time... plus I get the convenience of being able to go when I want to go since I'm not reliant on some MTA that may not be running efficiently that day, assuming the time I want to go is even in their operating hours.
Oh, and my local stores are so high priced, it's generally cheaper for me to get in the truck and drive for better pricing. Last summer, I did a project and it was $14 for a sheet of drywall locally versus $8 at the big box store 25 miles away. At $3/gallon and 22-26mpg, buying two sheets breaks even and anything more means I'm saving money by driving. Take my truck away, limiting my options and you don't think the local stores are going to charge less for their goods, do you? There aren't going to be many extra local jobs either, since the local lumber store isn't getting the bulk discounts of the big box stores, so most of that money travels out of town to the distributor/manufacturer anyway. Further, I'll have less money to spread around for other things I need, which means my quality of life goes down overall.
Modern travel and shipping (in addition to industrial manufacturing) is what enables our vastly higher quality of life versus our 19th century breathren, including shipping to cities, which are entirely unsustainable on their own/are completely reliant on outside goods for their entire existence - power, water, food, building supplies, raw goods, etc are all fed into a city and most of those things come from the rural counterparts that you want to limit in the hopes that they'd adopt your lifestyle. Simple fact is, cities die without rural people doing what they do, yet, somehow militant urbanites think the rural people should be punished by having to do without the benefits of modern society. I say let people live where they want to live, how they want to live and stop trying to force everyone to live the way someone else decides they should have to live. If they want to deny rural people cheap travel, I think rural people should deny them cheap food, water, gravel (used in asphalt and concrete, both of which cities love), lumber, coal, ore, etc.
If you want to interfere in the lives of others, you should expect everyone else to have the right to interfere in yours. I'm not your property, so don't tell me what's best for me or how I should live just because I value different things than you do. And please, cut the corn subsidies for rural farmers, oil producers, etc if that's where you want to go for your argument that travel is too cheap. In fact, cut all the subsidies, including the millions and billions regional/state/federal governments take from outsiders for urban pet projects, since that is precisely how we use the government as a means to force others into doing what we want but refuse to pay for ourselves. "Government oughta" is a pretty evil path to go down, even with the best of intentions...