Any particular reason why they thought it was a good idea to cut certain things out of the PS2/Wii versions?

Hunch, but I'd just say 4.7 Gigabytes isn't enough space for that sort of things. :P

They could've use a double layered disk like Smash Bros Brawl. But I'm hearing that Wii/PS2 production started later than the 360/PS3, so you know, when you're pushed for time.

they actually added things to the Wii version. You'd be surprised how much extra programming they'd have do to make 3 or 4 ways to play, full motion control, hello. For PS2 it would take way too ong to load a level, look at GH3 no PS2, it takes forever.

I think they started with the PS2 version of the game, then modified it for the Wii. The Wii probably could handle something closer to the 360 version, but I guess they didn't have enough time to make that.

So it's not that they cut things from the Wii and PS2, but added things to the 360 and PS3, right?

From: DT-Fox:
"They could've use a double layered disk like Smash Bros Brawl. But I'm hearing that Wii/PS2 production started later than the 360/PS3, so you know, when you're pushed for time."
They actually only have to make one master copy of the game to begin with, then they more deeply encode it to work differently with different systems. You can tilt the PS3 controller from left to right, they might use that to steer, that's the different encoding.