LOL. If you're a row cropper, you're running a big combine. Several grain trucks. Lots of expensive gear. Gear breaks down, that's why you buy something reliable, that has techs in your area who can fix things quickly, with a parts network that stocks stuff from decades back.
Farmers are self-sufficient in incredible ways, but maintaining a multi-million dollar combine is pushing it. They can do oil changes, filter changes, replace consumables on implements, and do basic trouble shooting, but there are limits.
And yes, time does matter. That's why farmers tend to help each other out a lot. Field catch fire because you didn't clean off your combine the previous day? It's going to be your neighbor coming out and helping firebreak your field so you lose 5 acres instead of 500. Can't afford to have your own sprayer for fertilizer, etc? You hit up the co-op.
And farmers have crop insurance. Doesn't make them whole, but the idea that they're going to be eating dirt if they harvest a day late is silly.
> but there are limits.
Even without limits, you're never going to be as efficient as someone who fixes the same failure every single day. I've certainly fallen into that trap before. Sure, I got it fixed myself in the end, but in hindsight I'd have been back in the field a lot sooner if I had simply brought in the expert. When time is of the essence, putzing around trying to fix it yourself is not the optimal choice.
And that's not even considering the need for parts. Driving all the way to the dealership and back to get the parts you need is much more time consuming than the dealership tech bringing the parts with him when he comes. He only has to travel half as far as you do.