You can't be forced to by insurance from one agency. According to the people I have talked with (dealers and friends) Kubota only offers the insurance because they want us to keep buying Orange. I guess they figure giving us cheap insurance that covers everything could be the thing that keeps us coming back and it did work on me. Like I said, I had a claim last year and it was easy. I still think using your home owner policy is a mistake but I hope no one has to find that to be a fact (one claim and you could be looking at an increase in cost if not lose your home owner coverage). Skip
But it DOESN'T cover everything.
Kubota offers insurance inexpensively for two reasons. One, it ONLY covers physical damage to the tractor, for which there is a minscule number of claims, and they are ALL small claims(in the insurance world, even replacement of your tractor is very, very small). A very small percentage of those claims are total losses, and remember, you'll likely get depreciated value, otherwise known as actual cash value.
The second reason Kubota offers cheap insurance is that they want to be sure there is an outlet to provide said physical damage only coverage to protect the interest of the lienholder, most often, Kubota credit. They don't care about your exposure to property damage of others or bodily injury, that's why they don't offer to cover it. That and the fact that the real large claims in insured losses are liabilty ones.
I wonder if the increase in cost that worries you so is greater than the annual year over year cost of a seperate policy issued through Kubota? Generally a single paid loss may cost you the loss free merit credit on your homeowners policy, and in the majority of cases that is less than $100, maybe a lot less. Let me ask you this: Is Kubota Insurance an admitted company in your state? If not, it's surplus lines, and probably subject to much less regulation.