Keep in mind that recognizing an online seller as "sketchy" requires a great deal of technical skill all by itself. To the average Joe, there's not much difference between eBay and Amazon. Hell, I just searched for "kodi" on Amazon and turned up a ton of stuff there advertising free movies and TV shows. Amazon! You want to tell me that the average person should see something sold on Amazon with Prime shipping that says you can use it to stream movies and TV for free, and understand that this is not legal?
Are normal people supposed to expect companies that advertise out in the open like that to not be legitimate? And I mean... they sort of are, they can deliver what they're advertising, they'll come to your house and set it all up and even give you support. Most consumers wouldn't know (or likely even care much about) the difference.
It never even occurred to them that it was piracy. When they thought of "pirating" or "theft", a glossy site that their friends told them about, and that asked nothing of them wasn't it.