Flashing of the player sprite comes from very early platform games which were released on extremely low-powered systems (such as NES or Atari 2600). Therefore the only visual effect available was to flash the sprite character on and off. Modern systems could do much more, such as surrounding the sprite with a flashing gold halo but, strangely, games usually stick to the same old visuals (which can result in the player momentarily unable to see their character).