http://www.breachbangclear.com/shot-timers-no-metrics-mediocrity/

These same pundits rail against scored drills, calling them meaningless measures of precision. Actually, scored courses or drills serve many important functions and are critical to development as a defensive shooter. Here are some of the reasons they are important.

1. We need an objective view of the student’s skill, not a subjective view. The target and timer don’t lie.
2. We can compare the student’s performance to a historical standard, set by measuring the performance of a number of students before him. Thus, we know if we need to remediate or move forward.
3. We can precisely quantify and track progress, essential to skill building.
4. We can instill the timing issues necessary for shooting at the right cadence as target size/distance varies.
5. We can get the student accustomed to working under stress.
6. We can help the student build confidence. Not measuring skill leads to false confidence. Students always think they are doing better than they are. Actually scoring, and incorporating both accuracy and speed in the scoring, shows true skill level, and allows real confidence.
7. Training and practice build skill. Skill builds confidence. Confidence leads to coolness. Coolness prevents panic. This is what wins fights.

In the extreme stress of a real life shooting incident, skill degrades. However, the more skill one has, the less skill one tends to lose (see #7 above). The less skill one has, the more skill one tends to lose under duress. This is why “good enough” is not good enough. Also, the Mother of retention of any physical skill under duress is structured repetition. To have a higher skill level, one had to practice more (structured repetition). I have debriefed a number of people after shootings, and not one of them has ever said to me, “When the bullets starting coming my way, I wished I hadn’t trained as hard.”