Flat pedals are ideal for those not wanting to use a clipless pedal system, they provide a large grippy platform for normal shoes to grip too. You can fit toe clips and straps to some flat pedals to benefit from pulling upwards when pedalling on hills or accelerating, these tend to be more for road/commuting use. Generally the main use for most types of this pedal now is Freeride or Downhill where quick placement and removal of the foot is essential.