Why do quantum researchers talk about coherence time like it's the most important metric?

[FrostDrifter]

I keep hearing about coherence time in quantum computing. What is it and why do quantum people care so much about it compared to other metrics?

[Tel86]

Coherence time is how long a qubit maintains its quantum state before decoherence happens. It's measured in nanoseconds to milliseconds depending on qubit type. Longer coherence time enables more computation before errors dominate