Triggering events to crash opponents wasn't powersup based, plus it was to crash the ppl behind you (to get away from police).
And it was very very limited.

What s/s is doing is really completely different, since you are essentially firing the enviroment at your opponent, plus s/s powerplays change the tracks/create shortcuts.

And it's not limited at all, I can have 2 route changes, and a shortcut in 1 lap of a 3 lap race, that's 7 powerplays.

It all just depends on the car you are using.
Cars with a high drift rating build up meter like crazy by drifting at high speeds. Speed based cars are better for drafting cause they can keep accelerating, to the point of just pushing your opponent forward.

They also build meter pretty fast when drifting at very high speeds, but they tend to be very unstable when doing so.

Also take more risks, the close miss bonusses build up meter pretty fast too.

I do agree on having a boost option though, it could've made the game a bit more complete. But I guess they wanted the focus on powerplays, and not just burning meter for boosting.