IMHO:
1) I wasn't worried at all about the Ram's WR corp until Bailey's suspension. I figured rolling the dice on either Britt staying healthy/clean AND/OR Quick developing the ability to separate AND/OR Bailey developing into a gamer--getting a favorable roll on at least one was pretty good odds. Since Bailey's suspension will hurt his development, not to mention his standing with Fisher (see Jo Lon Dunbar)--the odds have been reduced to something less than favorable.
2) With everything the Rams did in off-season, it's clear the Rams have shelved the fans' hope of becoming the next generation of The Greatest Show on Turf. Robinson-not Matthews/Watkins, Mason-not a WR, Schottenheimer-not any other available OC, Defense, Defense, Defense. With Mason and Stacy successfully running the ball 35 times a game and a dominant defense, the need for an elite receiving corp is somewhat diminished, no? It worked for Seattle and San Francisco and Fisher has clearly jumped on that ship.
3) Ball control is what Schottenheimer does best, which is why the Zac Stacy emerged last year and the Rams played respectively after Bradford went down. Bradford's injury forced the Rams to go to a ball control offense. The pick of Robinson and Mason clearly shows that Fisher and Schottenheimer are thinking ball control first with the ability to quick strike through the air at a moments notice.
4) The name of the game in ball control is field position, which requires a dominating defense (check, by adding Greg Williams, Donald, Joyner) and elite special teams (big check if and when they get the penalties down). Take away the penalties, add a year of experience and the Rams arguably have the best special teams in football (Minnesota and the 49ers can give good arguments).
5) Wasn't Tavon Austin supposed to be the answer for the Rams' game-breaking WR needs? At least that's what I heard a billion times before and after he was drafted (heard a lot of other crap, but let's ignore that).
6) Jared Cook also gives the Rams a powerful dynamic playing the slot. Too bad he can't block a limping girl scout as a TE, but I guess that's a different story.
7) Givens, with Bradford healthy, a good offensive line and a good #1 receiver, would be an excellent #2. He's very fast, stretching the field and he's proven he can catch underneath (see second 49'ers game, 2012). He was never meant to be a true #1 (see Tavon Austin).
8) Pettis is a Schottenheimer staple. He blocks well, has tremendous hands and runs his routes well. Name another receiver on the Rams roster that does all three of those? Bailey will in the future, I believe. TJ Moe, very well may (and why he was brought in). You won't see Pettis on very many highlight reels but he does bring a smile to Schottenheimer's face. Every time Austin or Givens dropped a pass or missed a block, or Quick ran a crappy route, it was Pettis trotting out on the field for a key play. If Pettis is cut, it will be because of the emergence of Bailey (now delayed) or Moe as Schottenheimers new security blankey.