The main reason is the SUCTION EFFECT !!!
Suction effect created by high speed air movement can pull us towards or even under the train !!!
Suction effect is also known as Bernoulli's principle.
When a train moves at high speed, it drags layer of air with it.
According to Bernoulli's principle, fast moving air between us and train has lower pressure than the still air surrounding us.
This pressure difference creates a net force that can push us towards the moving train !!!
It can lead to a fatal collision or pulling us into the gap between train and platform.
Watching a fast moving object at close range can cause vertigo. We may lose our balance and lean or Falk toward the track.