Whateveryeah - It's been going on for years, as far as I know. People don't like signing things - being committed in writing. I did a rewrite once for a producer. We negotiated the terms, it was a step deal. He gave me the first installment. I started the work. The contract never got drawn up for some reason, but I was getting my money so... I handed in the script, he paid me off. All's good. Let me back track - I went to his home to deliver the finished script and get my final payment. He told me that his partner in the project was suppose to give me the check this time. I said fine, but I'm taking the script with me. No money, no scriptee... Major uncomfortable moment. I stood firm and he came up with a check. It was a good thing.
My point is - if I trusted him and left the script, and then had to chase him and his partner for the money, without a contract I'd have no legal ground to stand on.
Also, he told me he had a few writers do extensive work on the script. He spent a lot of money, but was unhappy with the outcome. He gave me several drafts, same story, but all different takes. The red flag - the producer's name was the only one listed as writer on all the drafts.
Sorry for the rambling...