Originally Posted by FDru
PD is for carries
Triforce is for bruisers
Lichbane is for mages
I don't see the problem.
Also, mobility is nice but it's not everything. Out of the six highest mobility champs (Rammus, Kassadin, Nidalee, Teemo, Zilean, Udyr) only 2 of them are considered top tier.
Zeal is a cheap and quickly accessible core item that most AD carries, bruisers and tanks can fit into their build, and is part of both Phantom Dancer and Triforce.
Conversely, you only get a movement speed buff from Lichbane when the entire item is complete--costing 3,470 gold--versus Zeal's 1,195 gold cost. And Lichbane is a terrible choice for mages unless you already have a large pool of AP, whereas Zeal is a good early choice. And further, both Phantom Dancer (15%) and Trinity Force (12%) give much more movement speed than Lichbane (7%).
Basically all the top picks in Dominion (that aren't the stay-and-fortify-bot variety) have extremely high mobility, either from high base movement speed, AD itemization or some kind of steroid. A bunch of champions are either pigeon-holed into defending bot (if selected at all) or are never picked, simply because they're cripplingly slow and are at a heavy disadvantage to the top picks.