During the development of StarCraft, a two and a half year slog with over a year of crunch time prior to launch, the game was as buggy as a termite nest. While its predecessors (Warcraft I and II) were far more reliable games than their industry peers, StarCraft crashed frequently enough that play-testing was difficult right up until release, and the game continued to require ongoing patching efforts post-launch.

Why? There were sooooo many reasons.

Link