Hockey is a game of controlled chaos, with 10 armored men wearing metal blades on their feet chasing a small rubber disk across a frozen, slippery surface.
One of the main challenges associated with collecting data for hockey analytics is that someone (whether an NHL employee operating the league's Real-Time Stats System, a team employee or a third-party tracker) would have to watch the game very, very carefully in an attempt to organize hundreds of unique events into a few dozen distinct categories.
Every pass, shot attempt or turnover is a different snowflake, but to be able to gain any analytical insights into what is happening on the ice means pigeonholing these events into simple "outcomes.