The math nerd would be right Ray Allen is a good shooter. You can look over the course of his career and verify that. But that's not the issue with streaks in sports. The issue is that Ray Allen isn't a good shooter right now.

The idea that you "expect" something doesn't diminish its importance; especially when the Celtics need Ray Allen to hit threes to improve their chances of winning. They don't care that he's hit them in the past because previous scores don't count in current games.