I expect it depends on the particular company, but I have noticed that there is a direct correlation between having a fully-staffed accounts department and paying your contractors on the last possible day you can get away with. (I'm sure someone will tell me that "it's just good business," but it shows a lack of empathy with small contractors who may be operating on a tight margin).

I'm not entirely convinced there's a real correlation, just because my observations agree with yours, but they do: Any business with more than one tier of bureaucracy offers vastly more opportunity to pass the buck, offer plausible excuses, or play good-cop/bad-cop than a three-person startup does.