Those are insurances, really. If you're unlucky, they could serve their purpose but the risk is calculated for them as they are, indeed, a profit source. For one unlucky customer, they have ten or twenty that paid for "peace of mind" without barely using the benefits. Also, not all plans are equals (deductible, specific limitations or conditions, like using a specific shop for maintenance, etc). Personally, I rather put money aside during factory warranty in case something happen afterward. If nothing happen, I'm the one keeping the money instead of some insurance company. But for some the "peace of mind" argument is important.