I think part of it is when the arrived on the scene them, 3 Doors Down, and Creed became sort of representatives of the truck driving clean cut white guy rock that wasn't quiiiiiite metal. It was a joke in the rock world that if you wanted to sell millions and get radio play, just water down everything you do and pretend you didn't.
It just sort of came along through the years that Nickleback never changed and even sort of embraced the hate, and the fans loved them for it. People who love Nickleback will always love them because it's that person's way to "stick to the man." Kind of like juggalos only without the face paint (unless you count pick up trucks and goatees).
But really the joke's on us. Radio still plays this kind of rock music like crazy (Imagine Dragons and 99% of what you hear on 93X), and the "real" rock music is all but gone from popular culture. Outside of screamo emo post hardcore whatever, the rock music most people hear every day is pretty tame and not very creative.
And yes yes yes, before people talk about radio being a bad barometer, in the 80's/90's we had MTV to help us find new music. We were thrown outside of our music comfort zones quickly just by turning on the channel. Now that MTV "doesn't exist" people are more comfortable sticking to what they know unless something (like Psy) goes viral. Let's face it, the average 20 something will Spotify their channel based on the favorite bands, and not really hear anything that will change their music preferences dramatically. This gets worse when you're in the 30's and 40's. This is the same as listening to radio in the 90's and 00's and a bit today as well. Even The Current who is known for expansive experimentation isn't anything like Radio K and will stay within the comfort zones of their listeners... "Now here's some heavy music from the Ramones!" And Radio K? Well they break the mold obviously, but still have some standard on what they won't play (it seems).
Sorry, wall of text... but as a 40+ year old who's watched music grow and change in the last 30 years it's amazing how certain things just HASN'T changed despite all the technology that we have today.