I think it's mostly an issue of trust.
- Customer says they can only pay in 6-months time? Ok, you will route around it.
- Customer says they will pay next month and then ghosts you for several months? That's not cool. Particularly when it's peanuts for them, in the grand scheme of things.
I was personally burnt by the latter scenario. It was only resolved when they reappeared almost a year later, after I had stopped consulting altogether, asking me to find some other guy to carry on; I replied that I couldn't honestly recommend my peers a customer that doesn't pay, and lo and behold, two weeks later the money came in.