Why is "Rock and Pop" labeled in the same category lol?

[wil]

....first time getting a yahoo answers acc and noticed the rock and pop cat.
What is up with that? I seriously find that an insult. xD....to rock \m/(-.-)\m/

 

[Elliott]

well for starters theres a ton of overlap between the two!

 

[Janey]

because pop (all variations) is one of the three tributaries of rock music.