This ensures you, the original owner, can get service without the need of a receipt later down the road. It's similar to voting registration in the US; you've proven at the time of registration that you've made the purchase so this card negates the need to prove it again.

Although, having worked in consumer electronics for 25+ years, if you're buying something from a trusted local dealer, be sure to ask them if you should register. They may be able to fudge the purchase date and warranty period for you if you need service.

Moreover, much of today's consumer electronics are so cheap and outdated within a year that most people just throw crap away and buy a replacement rather than get it fixed. I have seen some inexpensive products actually cost more to get fixed under warranty (if you have to ship at your expense) than to buy the replacement product.

Ironically, it's probably the case that I register the stuff I expect to last longer than the warranty. It's an easy way to provide the serial number and my info to the manufacturer and confirm if it's under warranty or not. It also registers you for things such as firmware updates or recalls. So, a $1500 camera, yes. A $30 battery pack, no. A $200 speaker bar, yes. I also save all my boxes because they're the perfect vessel for shipping if they need repair.