For example, rangers always start with medium armor, shortsword, bow. If you make a STR ranger (ranger knight) you might very well dump DEX to 8, and you're boned until you find some heavy armor and a decent weapon. For any class that can conceivably go STR or DEX this is an issue. It also matters for classes that might go two-hander vs sword and shield vs dual wield.
Even beyond power concerns, it's a fun start to customizing your character. A longsword vs a warhammer may only be a different damage type but it's part of how you distinguish your character as your own. You might have a cool concept for a Githyanki melee wizard but you're starting off with robes and a quarterstaff like everyone else. I understand holding back more exotic options to be found in the world, but please give us some choice.
