I'm not seeing how the GP's idea could be used by bad guys to block access to services - it'd be something you could add to your firewall, if you don't use this service, to prevent it's use in gaining persistence.
If the bad guys can modify your firewall config, you already have a problem.
Federal subsidies may contribute, but average farm size has increased, and employment decreased, over a much longer scale - century plus - than any farm program I'm aware of. It's a massive secular trend longer than the monetary items mentioned as well.
Technology/automation is a commonly cited cause, although in this context you'll see references to mechanization.
If the bad guys can modify your firewall config, you already have a problem.