The reason is that the WWE itself - through its onscreen booking of authority figures and its off-screen perception by smart fans – is the biggest heel the company actually has.
Wrestling fans in 2017 hate nothing more than being told what to like, so as soon as it became apparent that the "machine" was behind Roman Reigns, it was over for him with a large segment of the audience.
Painfully transparent booking like Vince and Hunter being in collusion to stop Roman Reigns from winning the title (fucking really?) didn't help, and having idiots like JBL and Peter Rosenberg whine about how great Roman Reigns is and how stupid people are for booing him just makes matters worse. They think this stuff helps. They think the more people that come out and tell you how great Roman Reigns is, or the more Hall of Famers who tell him it's "his yard now", that all of the sudden we'll all magically wake up one day and go, "fuck man, you know what, this guy really is just the greatest."
Fans today are too "smart" to the business for that kind of booking to work. So no, it's not for no reason, there's a perfectly valid and legitimate reason for it.