It’s not that the frames blend in the screen. Screens are perfectly capable of switching the pixels fast enough. It’s rather that each frame is displayed for to long.

In a CRT the “pixels” start to fade immediately leaving the full screen mostly dark as the beam sweeps over the screen. It never shows a full frame.

One could say that modern screens are more like slide shows, while BFI tries to make them more like stroboscopes.

The blurring effect is more pronounced ate low refresh rates, its just that BFI requires at least 120hz to male sense at all.