I think even SNL realizes how overrated he is, so they don't want to hype him up any further than this...Besides, it's the Valentine's Day episode, only fitting that they bring in the flirty pop singer...Actually, they usually give the "pimp spot" treatment to rappers, R&B singers and classic rock musicians, because rap and R&B represents the monarchy of popular music today, and classic rock is that of yesterday.
Just to clarify, look at the last handful of episodes of Season 35, Season 37 and the first half of this season:
There tends to be alternative at some point: Them Crooked Vultures, Jack White, Muse...
Then slightly softer rock music: Vampire Weekend, The Shins, Passion Pit...
Teen pop (or sometimes just pop): Justin Bieber, One Direction, Bruno Mars...
Indie: MGMT, Gotye, Fun...
A female R&B singer: Ke$ha, Rihanna, Rihanna again...
A male R&B singer or rapper: Jay-Z, Usher, Ne-Yo...
And then finally an old-timey rock musician: Tom Petty, Mick Jagger, Paul McCartney...
Overall, I think the line-up of each season is getting a little too predictable...Hopefully, they change all that for the remainder of this one...I mean, I think with Mars and Bieber, they pretty much used up their MGs for the teen girl demographic...Unless they want to bring in The Wanted, but I really see no point since they're already bringing in Bieber...