Why do some SpaceX launches have such narrow launch windows?

Answer: Because orbital timing, weather, and safety constraints all have to line up

Because orbital timing, weather, and safety constraints all have to line up ✓ — Correct! Narrow launch windows usually happen when several constraints stack together: the desired orbital timing, weather, range safety, and sometimes booster recovery or rendezvous requirements. The exact main constraint depends on the mission.

Because satellites only work during one brief daily signal burst — Wrong. Communications can matter for some missions, but they are not the usual reason for a narrow launch window. Most often, multiple timing and safety constraints have to line up.

Because fuel can evaporate or leak if they wait too long — Wrong. Propellant loading does create countdown constraints, so this misconception sounds plausible. But it is usually not the main reason a launch window is only a few minutes; mission geometry, weather, and safety rules matter more.