So you think the parents of younger employees should subsidize Walmart's business?

Even if you say that's fine, there's a deeper problem.

Let's look at the most recent census: as of 2022, there are about 20 million people in the US between the ages of 15 and 19. Now that particular range is a little young, but that's the breakdown the census gives us; and the cohorts on either side are about the same, so we can probably assume pretty safely that there are also about 20 million people in the US between the ages of 16 and 20 as well.

Since the end of the pandemic, about 20 million people in the US are getting paid below the almost-living wage of $15/hr. Cool, problem solved then, right?

Except no. The demographics are all over the place. First of all, not everyone between the ages of 16 and 20 are employed full time; in fact, almost 60% of them are not. Which means that, of those 20 million people making below $15/hr, only about 8 million are kids under the age of 20 who could reasonably expect to be able to live with their parents. Which means that 12 million of the people who are getting paid less than poverty wages for full time work are fully adults. That's five percent of the US population.

"Ok so get roommates" you say. But the housing stock isn't set up for that; in order to pay appreciably less in rent, you have to cram more than one person into a space originally only meant for one; often this is not allowed by the property. Plus, when you're talking about people over the age of 20 (particularly once you approach 25), you're increasingly talking about people with children; particularly in the demographic that works at a low-wage hourly job. In most cases, including roommates in that scenario would be inconvenient at best; and prohibited or even unsafe at worst.

"No one could work at a convenience store and support a family alone" you say—but again your assertion doesn't line up with reality. According to a BLS report from 1975, "basic rates for grocery store employees averaged $5.19 on July 1, 1975"—that's $29.46 in today's dollars, and about 75% of the median household income across the country. Couple that with the fact that housing prices adjusted for inflation have more than doubled since the 1980s while wages have stagnated (median household income in 1970 was a little over half of the median home price; today it's less than a fifth), and you see that, yes, a head-of-household could indeed have supported a family on a grocery store worker's income. It wouldn't have been easy, they wouldn't have lived in luxury, but they would've been safely lower-middle class.

It's also important to realize that when it was originally proposed, the minimum wage was intended to be a living wage. Roosevelt said, "It seems to me to be equally plain that no business which depends for existence on paying less than living wages to its workers has any right to continue in this country. By 'business' I mean the whole of commerce as well as the whole of industry; by workers I mean all workers, the white-collar class as well as the men in overalls; and by living wages, I mean more than a bare subsistence level—I mean the wages of decent living."

(Sources are CPI, BLS, and the Census Bureau.)