Justified Expectation of Pleasant Surprises
I'm surprised how many people justified seeing all the options ahead of time because they weren't allowed to cheaply change their mind later.
The way Diablo II's full information, no take-backs system rewards intentionally gimping your low level character is terrible. A game should be fun all the way through - you shouldn't avoid putting points in flare because fireball is coming up, and you shouldn't need to avoid lightning because more important endgame monsters are lightning immune. On another level, games shouldn't be presenting you with so many bad options masquerading as viable choices. Too many character builds in D2 will make it through normal difficulty, whereupon harder difficulties (and the remaining 2/3s of the levels) are impossible to complete. Games should not be punishing you like this.
The simple implementation of an inexpensive way to reorganize skills enables games to give the pleasure of discovery and the benefit of planning.