Why? As is hardware function of monitor and required for monitor to work as designed.
You don't seem to understand that turning it off is only going burn your hard ware faster with no gain at all. If your monitor is 60Hz then it CAN NOT display over 60 frames per second. If you turn off Vsync a FPS tracing program will detect above sixty FPS because that's what's being generated by the graphic card however it won't look any different on the monitor at all.
A simple google search would have answered your question.https://www.google.com/search?q=monitor+turn+off+vsync