My favourite example of this is when I get ads for something that I’ve just recently purchased and clearly no person would want more than one of. Just bought a waffle maker? Why not buy another identical one? Never know when you’re going to need a backup right?
I'd totally understand that when you're returning the waffle maker and they're like "hey, that one probably sucked, here are 12 others", but yeah, it's weird. And that's coming from a guy who absolutely does buy backups of the things he likes, because how would I survive if my electric foot warmer would die and I had to wait 4 days for a replacement?
Or worse than having to wait for the replacement, by the time you need to replace your favorite foot warmer the product has been discontinoued and all the available alternatives are worse or at least different enough that you have to spend time figuring out which one is best for you.