> There are an enormous number of marketplace norms which prevent being able to make demands on a customer like that
There's also the reality that every business is on a 30, 60 or 90 day phase lag from delivery to getting paid, and so they have no choice but to enforce those rules up the supply chain. If you don't you need piles of cash upfront months before you generate any revenue, at scale that is really tough to manage and there's a very real cost to money.
The simplest example of this I can offer is that if you have to borrow ten million dollars to pay all your suppliers upfront and this money cost you 1% per month (making the numbers simple for the sake of an example), you are going to incur a 5% cost of money if you have to wait five months to get paid (again, keeping numbers simple).
I have a friend in the production business who made commercials for a major animation studio. He told me it typically took them about six months to collect. They would invest massive amounts of money on equipment and personnel to shoot, edit and deliver a commercial and their payment would not come for six months after delivering the end product. The entire cycle would easily have taken a year.