Agree this is a benefit, but in Louisiana's case this benefit is only 0.5% of their GDP (10 billion aid / 205 billion GDP). In a red state, where business interests more heavily control political power, I don't think federal tax benefits will influence a Brexit-tier decision too much.
To put this in blunt terms: there are a ton of impoverished African Americans in these states that receive a large chunk of that federal aid. The segments of Louisiana that don't receive that aid are tax-productive and will not vote against a Brexit-like decision, even if it means that federal aid stops flowing
> this benefit is only 0.5% of their GDP (10 billion aid / 205 billion GDP)
This is 5%, not 0.5%. On top of that, your numbers aren't correct: they receive around $20bn net, and their GDP is around $250bn, which means that which means that direct net federal spending is about 8% of their GDP (and gross federal spending is a whopping 20%). These are pretty huge numbers, and they affect the entire state economy, directly affecting the profits of the business owners that you claim wouldn't care.
To put this in blunt terms: there are a ton of impoverished African Americans in these states that receive a large chunk of that federal aid. The segments of Louisiana that don't receive that aid are tax-productive and will not vote against a Brexit-like decision, even if it means that federal aid stops flowing