Quoted from pinball_keefer:

Since when was it ever tried before? Probably not since the EM era if I had to guess. Some early SSs, too, but in those cases more often than not they were on shot paths (thinking Embryon or Flash Gordon here) than individual targets (Surf Champ for one example that comes to mind offhand). The last game that had a rollover I actually aimed for for a good reason was Stingray (and I won a PAPA classics because of it, too).
I have been on the record many times basically saying pinball has lost its soul playfield-wise. There's only so much you can do with shot-based layouts, and while it hasn't all been done, I can't think of anything particularly interesting that's been done recently in that department. Games basically spoonfeed players too much with flowing shots and everything coming back to your flippers all the time. Stern has attempted to fix that problem with magnets. I think the fix is in geometry.
There are several reasons the standups exist the way they do. One is that we didn't want to dedicate shots to specific characters, we wanted more icons and feelings from the movies. Shooting a shot a zillion times to spell something out is really really boring to me. With the rollovers, it just happens in playing the game. You can go for them if you want, and you'll get rewarded with getting to the main multiball much faster. Or, you can let it happen by having the game play itself, more or less. Think Funhouse here. There's no shot or shots to light mutiball, just having fun and shooting the game does it. Same toery here. This is extremely important especially for the casual player because they can feel like and see they made real progress just by keeping the ball alive. Hopefully they keep it alive enough and multiball happens. I like their chances better with the rollovers than making a single shot many many times. Finally, the rollovers are where they are to encourage the ball to be put into peril. This goes along with my earlier point about spoonfeeding, etc. The game is more exciting if you have to fight it and earn it a little bit IMNSHO instead of simply Paul Bunyoning a game to death.

Well, they're not rainbows, but Sorcerer's are pretty important. And you may notice they're not simply in a row, but they are curved, encouraging more, you guessed it, peril. They are an important part of the game (maybe not quite as important as Sorcerer's, but certainly up there), so we get some nice risk-reward and strategic decision-making as a result.
To me, one of the most remarkable things about the game is that on the ENTIRE bottom playfield, there is exactly one spot that doesn't score, and that's the rubber to the right of the spinner shot (at least the part that faces the player, not the part that faces the upper flipper). I think it's a great mix of important perilous targets/rollovers and extremely casual-friendly with the distinct lack of non-scoring posts.

Quoted from Pinchroma:

Actually flip randomly and you get NOTHING. Even if you manage to flail away and light the rollovers you still have to hit the ramp for each lock to start multiball. Thats a targeted shot. If you just are flipping aimlessly you aren't going to make those shots and certainly aren't going to make it to multiball.