Professional filmmakers often don't need the required permits either.
Turns out that the occasional fine one incurs for shooting without a permit is often cheaper than the cost of the permit itself. Even if the fine is greater than the permit, it still can work out cheaper, depending on how often you get caught in relation to the number of locations your production utilizes.
Fact is, unless you're in a part of the country where film production is a major industry, chances are very good that there aren't any local film production ordinances in play at all. Even if there is a local film commission, which supposedly regulates film production and issues film permits and the like, many of these commissions lack any legal authority whatsoever. Their rules, regulations, licenses, permits, etc simply have no legal basis, and there's absolutely no enforceable legal consequence for violating them.