Why do teachers need to be evaluated by metrics at all? Every professional (software dev) job I've had has managed to do a reasonably good job selecting and pr

Why do teachers need to be evaluated by metrics at all? Every professional (software dev) job I've had has managed to do a reasonably good job selecting and promoting the right people. Not perfect, but well enough. Why is teaching the only domain where adults are unable to make professional judgments about coworkers?