This can still be helpful in singles. I use it quite a bit. If you're fighting Ivysaur, and you suck her up, you get one fully charged solar beam. When you use it, it's gone, and the power is useless, so you need to get rid of the power so you get suck back. This helps. Really there are times when I just want to ditch a power because I think suck will work better in a given situation or I decide for that matchup it's better. Sometimes I take a power after suck just for the angle it sends the off at.
Also, if you lightly tap downtaunt, Kirby does the "Hi" from Melee instead of Brawl, for ultimate skill showing.
So imagine this. You suck up a Samus. You take the chargeshot. You charge it up, shoot her off the stage, run off, taunt cancel off the ledge (using the unique lightpress Hi for extra style points) to ditch the power, and use Inhale for the Kirbycide.
MAXIMUM HYPE