Sears was one of the original "major offenders" in the extended warranty business. I have had two friends who worked for Sears, whose sales volume was among the leaders for departments in which they worked, who literally were fired for not selling enough warranty extensions. It is an extremely profitable facet of business for them.
Unfortunately, the concept has spread to virtually all retail outlets so Sears can't really be held up as THE bad example any longer.
The current leader appears to be Hewlett Packard, with their entire line of inkjet printers. Their laser printers are trouble free, and virtually indestructible, but I must conclude that their inkjet printers are designed to fail from easily user-repairable designed-in defects, within six months of the end of warranty, and they refuse to provide part lists or other information that would allow user repair. This forces you to "send the printer in" at a fixed fee of about 50% of the original price of the printer - unless you have paid 30% of the original price for the extended warranty. With the original or extended warranty, they usually will send you a **replacement printer, which will be a "rebuilt/used" one. [Note: This rant has been delivered to the HP CEO, with "polite" reply, and subsequent follow up from their customer service people; but they seem to profit from present policies and are not inclined to change.]
** HP screwed up and one of my inkjets failed while still under warranty. They immediately shipped me a rebuilt replacement, which was DOA. They immediately shipped me a second replacement, which was DOA. They immediately shipped a third replacement that worked for exactly 13 months (the standard warranty had I bought it new would have been 12 months) before failing due to their designed-in standard defect. I have "modified" the paper path to continue to use it, and I believe I can replicate the failed parts using the flint-springs salvaged from two BIC lighters, which I will do iff necessary.
Extended warranties are extremely profitable for those who sell them, which strongly implies they are priced to greatly exceed the cost of repairs that will be made under warranty for most users. If, as HP has done, they make trivial repairs extremely and disproportionately expensive, they may still be almost necessary; but I'm resisting.