It's been so long since I've had a flat, I mean, like years, that I've quit wasting my time with a jack. A jack means you've got to carry around a spare, too, and a mat to sit on while you jack up the car. And a lug wrench. All for the slimmest of chances that I'd have a flat somewhere away from home, like on a trip, where I wouldn't be able to wait until I got to a town and had to call triple A (which I don't belong to) or some other such. So, I don't carry one. Never. Haven't carried one for a dozen years. Haven't carried a spare in that long, either. And guess what?
I've never needed one.
Now, if I lived where there were lots of nails or screws on the road... Nah. Been there. Car notices pressure differences and puts a notification on the dash and I check it when I get home.