In a nutshell, active noise cancellation can be considered to be one of the most important pieces of 21st-century technology.
The benefits that come from having a quieter airplane experience or not being disturbed by other sounds while reading or working cannot be underestimated. Those who are largely unfazed by airplane engines are simply more aware of outside disturbances, which can make it hard for them to focus on what's happening in the real world. Those who are overly sensitive to engine noise may feel overwhelmed or even sick when flying because it amplifies their level of stress and anxiety. Noise pollution also has an adverse effect on children's learning environment at school as well as workplace productivity.