I think this is a rosy view of (at least) the 1980s-1990s. There were definitely jobs that paid way below what it cost to live, and there were plenty of people who needed to take a second or third job to survive. It just wasn't the norm like today.
Frankly, the biggest reason for these sentiments is straight up false nostalgia. The 90s wasn't some utopia. There were plenty of shit jobs. People struggled. Notice how none of the positive vibes are backed up by numbers. It's just "people owned houses and cars by working at grocery stores." No mention of how many people managed to pull that off or how it compares to today. It's just a vague feel-good statement that The Past Was Better.
I didn't back up my statements with numbers because I'm old enough to have lived through the times I'm talking about and it's as obvious how much things have changed in my lifetime, but here:
The 90s wasn't a utopia, but also, look at the media landscape of the time as a reflection on society - Fight Club, Office Space and American Beauty were reflections on the unfulfilling banality of life being too easy to find purpose. Married with Children (1987) and The Simpsons (1989) center on men who are supposed to be relatable-losers in low status, low paid dead end jobs (shoe salesman and power plant worker) and yet both have two story houses and are supporting multiple kids, because that was just normal and relatable to the blue collar average Americans watching the show at the time. Rocky (1976) has a protagonist who owns a house in Philadelphia despite being "poor", if it were filmed today they'd have to make him sleeping in his car for the character to represent the same level of desperation that audiences understood him to be in at the time.
Living through it doesn't save you from having a selective view due to only seeing a tiny, tiny portion of the country, or just rose-tinted glasses.
I've seen The Simpsons argument brought out a lot and it's weird to me. Homer isn't just a power plant worker, he's a nuclear safety technician, which pays quite well. Despite (somehow) having a really good job and a pretty moderate lifestyle (no childcare costs, modest and rare vacations, eating out infrequently, no fancy toys or extracurricular activities) and having substantial financial assistance in buying their house, the family is portrayed as financially struggling.
I'm not convinced about the usefulness of those numbers either. The figure for houses is probably useful. Used cars seem much less so. Modern cars last way longer. The average age of cars on the road today is almost double what it was then. The average price is going to be skewed upward by people with more money buying used cars that still have a ton of life left in them. Cheap used cars are still available and you probably get a much better car today even at the cheap end of the scale. For tuition, I'd like to see how financial aid changes the picture, since it seems like colleges these days engage in massive price discrimination by listing high tuition that few students actually pay in full.
Certainly some major things have become more expensive, but "there really wasn't such a thing as 'a job that doesn't pay enough to live on'" is way over the top.
