Cost and time both - which is of critical importance to farmers because, y'know, if the tractor breaks down as you're trying to get the harvest in before a storm front shows up and ruins the crop in the field, there's a -little- bit of time pressure and waiting for a Deere mechanic ain't exactly an option in those cases.

Ultimately, though, the whole situation's basically Deere trying to exert post-purchase suzerainty over the farmer's equipment, so they can continue to extract money from the farmer even after they've paid for the tractor.

This applies to a lot of things these days, as vendors are realizing that if they tie essential functions of equipment to "the cloud" that they force the consumers to keep interacting with them - at least providing opportunities to sell "upgrades"; at worst to induce artificially shortened lifespans on the products to force more money out of 'em.