For incandescent bulbs the power drop around the zero voltage cross doesn’t last long enough to extinguish the filament, since it’s basically just glowing from being heated. The only lights which actually do “flicker” under nominal conditions are old ballast driven florescent lights. Most modern LEDs rectify the AC and modern CFLs boost the line frequency to like 20kHz to prevent the arc from getting extinguished.
For incandescent bulbs the power drop around the zero voltage cross doesn’t last long enough to extinguish the filament, since it’s basically just glowing from being heated. The only lights which actually do “flicker” under nominal conditions are old ballast driven florescent lights. Most modern LEDs rectify the AC and modern CFLs boost the line frequency to like 20kHz to prevent the arc from getting extinguished.