Rock is dead? Because it's not mainsteam or on American Idol doesn't mean it's dead.
What defines suitable? What's in the lyrics?
Lyrics are a part of it, but that's not exactly what I was talking about.
Suitable, in this context, means a performer that would be good for the super bowl-- a somewhat family program viewed by 100 million+, the biggest stage in America.
Meaning the performer needs to:
1. Appeal to a very wide demographic.
2. Has to be somewhat upbeat and fun. (Adele is a highly regarded performer, but no way is she suitable for a SB halftime)
3. Should not be a polarizing figure.
4. Cannot be risque in their performance-- meaning subsequently their fame couldn't have been built on that stand as well (think Lady Gaga).
---addendum to 4, unless said performer is a legend, which brings me to...
5. Has to have had some kind of staying power-- a proven track record.
6. Has to be a relatively well known performer
To summarize, you have to have a safe pick.
What Rap/Rock acts fit those categories? With relevance to the criteria, both Rap and Rock aren't fielding any good candidates, hence Rap/Rock are kind of dead for this category.