Well, some people just don't have that musical "gene" in them. But they enjoy the music and pseudo-playing it, is fun for them. I think it's more fruitful than shooting people with a massive arsenal of weapons in a game [it's not that I don't do that sometimes, but yea

]
I've played RockBand bout 15 times now. It's fairly simple to get better and end up with a relatively high score. Now, let's see.. my 15th time playing the guitar, I was probably making the most horrid noise in the world while playing a simple intro.
Plus, it's a fun
group game. Lots of fun.