Business owners don't hire unnecessary people out of the goodness of their hearts. If they're paying someone full time to sweep floors, it's because it's a necessary business expense. The owner hasn't the time nor the inclination to spend 8 hours a day doing that person's task. If they can identify slack in the person's job, they will try to cut hours, but barring that, they will keep that person employed at a higher salary, raise prices to maintain profits if they're able, and all of their local competitors will do the same, as they are in the same boat.

That’s observably false. I have commented before that I choose not to hire an assistant any more because I am intimidated and overwhelmed by labor regulation compliance. There are many, many, marginal jobs like this. Jobs that could serve as an entry point to an industry for a person, and a business owner might happily hire someone and give them a chance to learn on the job, but if faced with too many hurdles, will simply do the work themselves.

This has the effect of making people even more dependent on college, btw. And can effectively make certain types of career paths disappear entirely.

Thing of a greeter at Walmart. How easily can Walmart just do away with greeters?

This is fair point. Adding a little bit to it

1. There exist jobs that are not worth paying someone X/hour, but are worth it at some number less than X. For the purposes of this discussion, X is "a livable wage".

2. There exist people who work, but do not need to X to survive; retirees who just want to be out of the house, mentally handicapped individuals for whom being out doing work and meeting people is helpful, etc.

Those two points are facts.

Requiring that every job pay a livable wage means that the combination of the above two will no longer be available. Those jobs just will not exist if they need to pay that much. As a result, some subset of group 2 will no longer be able to work (this part is opinion, but seems a reasonable conclusion).

So, the tradeoff is being made to make live worse for some of those people in group 2... in order to make life better for people in a different group. That may or may not be a good tradeoffs. But just the fact that it exists as a tradeoff means that "no job may pay less than a living wage" is not a black and white topic; there's a grey area.

What's the career path of a Walmart greeter?

it's not set in stone, and that's part of the beauty of it. Who are you to say whether or not another person may take such a job at a wage they find agreeable?

How many people do you employ, out of curiosity? And how has your experience been with labor compliance in your region?

Several in fact!

But to take your implication head on, I once worked for a company whose owner decided to do this stuff himself.

It resulted in several instances of people going unpaid for a few days and the owner sending out an email basically saying "if you don't get your paycheck on this friday and need money, come talk to me, I'll fix it".

The result?

The owner finally started paying someone who was competent enough to ensure everyone got paid on payday!

These laws exist for a reason, and those reasons generally involve people being affected by it.

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My learnin's from watching all of that happen is not to take it lightly.

Not every single employee is necessary in the sense that the business would go bankrupt without them. (Even if that were actually true, the minimum would drive some businesses into bankruptcy, so I don't see how it would help your case.) Rather there's always a choice on the margin. The business can sweep the floor every day, every other day, twice a day, etc..

As a software developer, if I were asked to sweep the floors I'd probably find another company to work for.

Or maybe not depending on how much I cared about the company, but most likely I would.

So for these companies, it's required.

The assumes that demand stays the same with increased costs, or that supply remains the same under entirely different conditions.

"And presumably when that $8 per hour worker gains experience and can provide more value, he either gets a raise or goes to another job that will pay what his skills are worth."

That's a mighty strong presumption to make. What skills exactly does one build up sweeping floors? And who is going to be incentivized to give out raises, when they could just hire a new person at the base wage?

Every year tons of new Javascript developers graduate from colleges and bootcamps. Why do any of them get raises when companies could just hire at the base wage? Sweeping floors may not be very exciting but you can learn skills - perhaps purchasing (supplies), handyman work (path to union labor), maybe the CEO notices the floors are freaking spotless and this guy has never been late once in the past year and decides to give him more responsibility...

JS developers are entering a growing market that constantly needs dramatically more developers than currently exist. This is not going to be true for cleaners of restaurants in 2020.