I clearly remember these folks. They acted in almost exactly the same way as literary or artist agents; searching out opportunities for their clients, and setting up interviews, etc. As a hiring manager, I dealt with them frequently, and had friends that used them.
They used to make a lot of money, because they would charge a percentage of the rate they negotiated for you.
Nowadays, it looks like they have been replaced by "race to the bottom" sites, like Upwork, or these contract companies, that hire you at a fairly low rate, and shop you out for very high rates. You get to "enjoy" the crappy treatment most companies give to contractors, but at rates lower than the employees that sit next to you, shooting spitballs at you.
I encountered this, when working with recruiters, after leaving my last company. The ones that didn't immediately hang up on me, after finding out I was older, started trying to lowball me into being one of their contract shop employees. They would love telling me that I shouldn't ask for too much, "because of my age," before "generously" mentioning that they happen to have a contract shop that would be willing to do me the huge favor of "throwing some work at me."
It's a real slime-pit, these days.
The issue with managing the relationship just in code is if you ship a bug to break the relationship, you now have to manually fix your data, and if you want to find out when or where the bug was introduced, you're looking at commit history instead of a migration history. Same thing when it comes to making manual updates or adds in the db. Even if it's just on a dev stage, if your code makes an assumption about the constraint which isn't true, you can end up with bugs or exceptions on dev, which is also annoying. If you want to remove the assumption of the relationship from the code entirely, that would be more understandable, but not if instead it means replacing what would be an efficient constraint and join with a separate query.
"Don’t pick something that needs a pretty UI": What if I'm really skilled in UI dev and have a good visual eye? Or a friend happy to do some free mockups?
"In-person sales are very weird for the developer personality": there is no one developer personality, I wouldn't rule this out at all.
"You don’t want to be going around talking to actual humans.": this is almost never going to work for a startup. Actually talking to people (users, clients, integration partners) is probably the most important thing you can do as a founder.
Cryptocurrency is different. No government is able to steal your Bitcoins by printing some more colored paper.
Yes today there are issues with volatility, but conceptually cryptocurrency is better than fiat money for the reason written above.
But if you like getting robbed every year then of course continue using fiat money.