I’m probably not the one to respond to this question, but I will… it is a valid question.
For one, only the most major and catastrophic problems that can happen on a piano are covered by the manufacturer’s warranty… “defects in material or workmanship”; cracked soundboards, cracked plates, cracked pin block, loose veneer, etc; Plus, you would have to go through an authorized dealer (or piano technician) for that manufacturer to get any such major warranty issue resolved, or, in rare cases, the piano replaced.
The minor issues that plague most new piano owners, buzzes, rattles, sticky keys, etc… are not covered under the manufacturer’s warranty, and are usually taken care of by the dealer as a courtesy (not warranty).
So, it is wise to choose a local dealer with a good reputation and references so you can feel comfortable that any issue, warranty or not, will be taken care of. Usually, a reputable dealer will take good care of their customers, warranty or not.
Piano enthusiast and amateur musician: "Treat others the way you would like to be treated". Yamaha C7. YouTube Channel