Some substantial fraction of all pesticide and fertilizer release into waterways comes from cities not farms. Also a huge part of the non agricultural water supply goes to lawns. So while I empathize with the people who say that asking residents to stop watering their lawns to conserve water, but we don't do that for farmers, that's still quite an impactful action from the perspective of the city's water supply.

The farmer is filling up a tank or hopper with hundreds or thousands of pounds of chemicals that cost them a ton of money so they can't really afford to have it just sitting around. They know when they fertilize right before a rainstorm just how much money they lost. The feedback is pretty immediate. Some people would say this is sufficient to prevent problems, but we know that's not true. It discourages problems, but it doesn't prevent them.

Meanwhile your neighbor has a $10 container they bought last year and they'll need a new one next year even if they didn't use it, so who cares if I fertilize and forget to turn off the sprinklers? Hardly any discouragement at all. It's very open loop.