Yes it needs suspension! The point of Technic sets is to allow people to make mechanically realistic Lego models. Suspension plus driven/steered wheels is mechanically hard to do so it is a big deal when Lego does sets like this.
Aside from the replicating reality, the result is you will see the engine turn faster or slower, or even backwards.
Well, there hasn't been many motorised cars for this reason. One model in 4895 Motion Power had a bump-and-reverse function. But most of the time the motor is for a function, not to move the car. (On that subject, I have got my Technic Ferrari working as a RC car now! *wub* I'll post pics soon... )
Well the steering is exactly that; you turn a steering wheel and/or a separate wheel and the wheels turn. As for four wheel drive, that refers to the fact that all wheels are connected via diferentials (sometimes three) to the engine made of Lego....
Perhaps. Technic just doesn't do it for some people. Because you don't see the use in all of these functions I suspect that you may be one of them. ;-)