I guess you need to consider the purpose for which the machine is designed. A car, for instance, goes down the road. If it is abused, you can tell. A tractor digs dirt. If it is abused, you can tell.
An ATV is for ambling over hill and dell, getting scratched by trees, punched by rocks, fording 12" deep streams, and carrying slain animals out of the woods. Why would a company want to be on the hook for an extended warranty on a thing that is, by its very purpose, going to get destroyed. And if you aren't destroying it, you aren't playing enough.
A little bit of kidding there, but I think you get my fundamental point.