Warrantees are like insurance policies, if you never have to use them they aren't worth anything. There are lots of things that can go wrong that can cost big $ (like pumps and trannies) but if the policy doesn't cover them it won't help much. Review coverage carefully for exclusions and don't let the saleman pressure you. These things are big profit items for dealers and can be invaluable, or not, to you. I guess it's partly to provide you with some peace of mind.
Dan