As someone who was without a car for a while...

Have you tried using public transit for grocery shopping? Where?

Oklahoma City has 20 bus routes, which seem to run every 30 to 60 mins. Unless you're lucky enough to live right on a bus route that goes to those supermarkets, or happens to line up perfectly with a transfer to another bus that does, it's going to take forever to get to the supermarket via public transit.

I've done it (in a different, but seemingly similar city). You leave early to make sure you're not going to miss the bus, and then you wait. If you're lucky, your first bus isn't late and the second bus isn't early... If it's just one bus, you trip is hopefully only like 10-15 minutes (you've already spent at least that walking and waiting), and then you're there! You probably want to shop for about 45 minutes -- even if your bus comes every half hour, making it back to the bus stop in 20 minutes ( remember, buses can come early or late!) is probably not going to happen, especially given that this whole venture isn't something you're doing every day, and you've got to stock up! But not too much, because you've got to carry it back with you. Speaking of, easy-to-carry packages of toilet paper or paper towels are typically astronomically more expensive than the giant packs, wtf. So, you get back to the bus stop laden down with stuff, everything goes pretty well on the trip back, and it only took, let's say, an hour and a half! Yay. You're never buying ice cream again.

But, you didn't get enough for your family for the whole week. You do it all again two days later -- you could have waited a couple more days, but the restricted weekend hours don't work out, or maybe you only have two days a week where that 7pm-latest-bus-run isn't too late (assuming you're comfortable trusting the last bus to get you home). You head out again, but this time, your first bus is very late. Or your second bus never shows. Or you miss your bus home, the last bus of the night, and now you have to call a friend or Uber.

This is all if you're lucky enough to live anywhere where trying this even makes sense. This is assuming your schedule isn't entirely incompatible with the bus schedule, and you can afford to be gone for however long the ordeal takes (my grandmother is a retired nurse living with her friend, who has Parkinson's; my grandmother tries not to leave for more than about an hour without someone else to watch her friend).

The price of public transport is not the $ for the ride; that could often be accounted for simply by the price difference between convenience store milk and Walmart milk.

In many cities, public transportation is used nearly exclusively by 1) lucky people who live right on the most reliable routes, 2) unlucky people who have very little else to do with their time.

The other day, I missed a bus in downtown Seattle. I could wait 5 minutes for the next bus (different route) coming by that stop, but have to walk an extra block at the end, or wait 10 minutes for the next bus of the route I missed. I said fuck it, didn't take any bus, and instead grabbed a delicious lunch at a hole-in-the-wall place a block away. This is not an accurate representation of public transportation in most cities.