When I first bought my tractor had had it out on my land (20 miles from my home) by itself quite often. I checked with every local insurance company and none of them had a separate policy to cover it. I don't know why that is just what I was told. Those were some very nervous times driving out to the land and going around the corner just praying and looking to see if it was still there.
When I built a home and moved out here the tractor was added to my home owners policy. As long as I only use the tractor for my personal home use (non commercial) it will be covered for theft. If I take my tractor to my business and it is stolen there I have no coverage.
Just my experience... don't know if that applies everywhere.