I started thinking about this after reading that World War Z is pulling out of Philadelpha after the city's film tax credits were suspended. In most other industries who see their subsidies cut they'd grumble about it, then look at their equipment and warehouses and sunk costs and home mortgages and suck it up. But film production is fundamentally ephemeral. You do it till it's done. If you're lucky you can re-use some of what you've built for your new project, but every project is different.
There are other reasons to subsidize film production. Bringing attention to your area, for example, seems perfectly reasonable. New Zealand has attracted lots of tourism with its "perfect slice of Middle Earth". But spending tax money to "establish" a mobile project-to-project industry seems like a fool's errand.