Well. Yes. But we are not talking about 1 barrel here. We are talking about a lot of "barrels". It is just annoying to gain speed and then run into an obstacle again. The way RC1 handled it was nice. You just got slowed down a bit by a rock or something or the shock wave of something exploding set you back a few meters, that was it. You could use those explosions as a way to accelerate more or get a speed boost too. Like the exploding zeppelins and other stuff.
Otherwise if we make things fall onto the street as seen in one of the trailers, you are gonna have a bad time. You are gonna wait there forever because your car just can't move anymore, while the one who fired the rocket just wins the race.
I'd say we crush rocks without them doing much to our car, like get it spinning or something. Just slow the cars a bit down. But make crushing rocks fun. So you want to crush them.
Exploding stuff should be used to accelerate or slow down other cars.
There is also the possibility about making certain destruction change the track, but that is far away from implementation, I think.