voltage drops ( or changes in general ) may interfere electronic devices as well as frequency-changes ( I think you´ve got 60 hertz in the U.S. ).

And of course other devices being switched on / off that are using the same power-circuit ( circuit-breaker ). As well as devices using a coil ( like some lights, I didn´t find the english name for it, long tubes that are a bit flickering when switched on, often called "neon-lights", but neons are working with high-voltage ( above 1.000 volts ) ... )
Greetings from East-Frisia ( Northern-Germany )