Noworries and Scotty both have good points. Would you be able to purchase an extended warranty on a used car, after the original warranty had expired? Would it be worth getting? Boats have so much more that can go wrong with them and so much more opportunity for it to happen that it is almost surprising that anyone would offer a warranty in the first place. If insurance is available, the deductible is likely to be quite high as well. The insurance company won't want to be covering incidental dings and maintenance items, but will certainly want you to do so. If you bend your pulpit coming into the dock because your rudder got stuck hard over, they are going to find out that you didn't replace the worn quadrant sheaves and that's what made the rudder stick. They will then say that you didn't maintain the boat properly, and won't cover the pulpit damage. If you're going to have to maintain the boat in such a manner, nothing is likely to break, so insuring against breakage makes less and less sense.
If you want to insure against damage you might cause yourself (going out when it's too rough, plowing into a dock or another boat), the fewer claims you have, the less your insurance is likely to cost. Of course if you have no cause to have claims because you're not going out when its too rough, and you're being careful not to plow into docks or other boats, then you need such insurance less and less.
Overall, as Noworries and Scotty both hint, extended warantees are a great way to soon separate some people from their money.