I sincerely hope you never test this theory. I think many people in this thread are severely underestimating how little noise is needed to be disruptive in the early morning.

My local noise ordinance sets the maximum permissible noise in residential areas during off-hours (10pm - 9am on weekends) at 45 dB. That can be exceeded by 5 dB for 15 minutes, 10 dB for 5 minutes, and 15 dB for 1.5 minutes. Lawnmowers are an exempt source of noise during day hours only. I guarantee if you were my neighbor your mower would be in violation of noise ordinance at night.

Plus, assume some people are sleeping with their windows open. Especially in mowing weather. Windows open overnight may be the only way they keep their house bearable during hot days.