If windows didn’t have this hole, things could go from annoying to dangerous:
Pressure Imbalance: No way to balance the pressure, and windows could crack or fail. Big safety risk.
Foggy Windows: You’d be stuck with fogged-up windows, no view. Frustrating on long flights.
Increased Stress on Window: The outer pane would bear all the pressure, more likely to get damaged over time.
In short, the bleed hole is key for safety and comfort.
To see why it’s so important, think about how air pressure changes as the plane climbs. At sea level, pressure is high. Up at 30,000 feet, it’s way lower. Planes pressurize the cabin to mimic around 6,000 to 8,000 feet. But the outside pressure is still low, so there’s a difference that needs managing.