Most large companies have lost their ability to innovate and moved to a model of delivering small performance improvements quarter by quarter. Employees are often under a lot of pressure and busy with day-to-day activities that the help of freelancers is called in to supplement hands, brains, and most importantly distraction-free creativity.
As a freelancer, I try to accommodate the constraints of my big clients as best as I can. Reprioritise other clients, maybe work a few hours on the weekend now and then, trying to deliver the best work possible. Being flexible when some designs are considered "too creative". Working with my direct contact points usually works great.
Then comes the accounting department. The electronic invoice of my highly efficient and transparent billing system gets printed out on paper, send across to a central pan-European payment processing centre, where a clerk discovers an error (info that probably sat in the body of the email or on page 2 of a PFD that did not get printed), marks the error and mails it back in regular mail from a European capital to Tel Aviv. I provide explanation by email, which get printed out, send to the processing centre, and goes back to me by mail.
Freelancers are consider suppliers, not employees, and get the supplier treatment. You did not get that PO number right, hah, hah, perfect excuse to postpone payment to you. Got you! We expect you to be flexible and human to meet that deadline, we on the other hand can be as flexible as a brick wall.
Big suppliers can defend themselves against these tactics. They invest in the same SAP software, they employee accounting departments with people who have time to call and chase things, and - of course - they do the same thing to their suppliers. They get paid late, but hey, they pay late as well. And, the financing cost of delayed payment is anticipated and gets priced into the invoice.
Big suppliers are willing to tolerate this behaviour. Big fixed cost bases means that big supply contracts are required for survival. Freelancers don't have the resources to deal with this stuff, but also: freelancers do not have a big fixed cost base that needs filling. A good freelancers is probably 100% doing her art. A good freelancer has alternatives.
The big obstacle for large companies to innovate and be creative is the ability to attract innovating and creative talent: be it employees or freelancers. Giving your freelancers the big supplier treatment is not going to help.