Abilitease

The point of the abilitease is to give the player further incentive to play through the game.  Often the abilities that they are given at the beginning are not as advanced as those the player will get further into the game.  The Metroid series is notable for including an abilitease in almost all of its games.  This is because of the linear nature of the gameplay, which leads players from one quest to another, with each providing a recovered ability.  Other games have found other ways to work the abilities back into gameplay.  For example Assassin's Creed has you rework your way up the Assassin rankings to retrieve your abilities, and Star Wars: The Force Unleashed actually offers you a different, more advanced character, to play as in the beginning of the game.  While on paper the abilitease would seem aggravating, fans have yet to voice serious discontent about including it in games.