If you have a switching power supply brick for your tiny USB device, not really.
If you have a large spinning inertial mass like a factory motor or a power generation turbine, it's extremely important. Imagine a manual car transmission, but there's no slip-clutch, you need to perfectly align engine with the wheels rotating at 300mph, and the inertial mass you're up against if it's not perfectly synchronized is a freight train.
That's why generators trip offline in a blackout cascade if the frequency deviates out of spec. The alternative is your turbine turns into a pile of very expensive shiny scrap metal.
If you have a large spinning inertial mass like a factory motor or a power generation turbine, it's extremely important. Imagine a manual car transmission, but there's no slip-clutch, you need to perfectly align engine with the wheels rotating at 300mph, and the inertial mass you're up against if it's not perfectly synchronized is a freight train.
That's why generators trip offline in a blackout cascade if the frequency deviates out of spec. The alternative is your turbine turns into a pile of very expensive shiny scrap metal.