Never understood why. They're formulaic rock. Even Chad Kroeger admitted that they just make music to sell records. I've seen them in concert several times. They put on a good show, and I really don't hate their music. It was on repeat in my dorm and subsequent apartments in college.
The whole hate thing cropped up inexplicably in the mid 2000s, and it never really died off. It's like its own meme now.
That the meme has lived on so long is interesting. I’m not much of a heavy metal person, but my husband has a couple of their albums and I thought quite a few of the songs were pretty good. Never really got the hate thing. It’s not like they’re Springsteen or Journey... ;)