[david422]

Because you have to mouse over, wait half a second, then find and click the app you're looking for? I'd rather trade screen real estate for time.

[kibwen]

If you want to optimize for time, then use Alt+Tab to switch windows rather than clicking.

[zamadatix]

I forget the way to set it but you can make the delay down to 0 if you want. Lately I've been using Mission Control to switch to active ones and Launchpad for to switch to inactive ones though. Spotlight can be good too.

[moralestapia]

Huh?

Then forget about the Dock and use Spotlight, I launch whatever I need in less than a second.