It is not just Gambhir. Most left-handers cannot resist flashing outside the off stump. It is part of their natural game
It is a double edged sword. If it comes off, it is one off the most attractive shots to watch in cricket; case in point: Gower, Lara, Saeed Anwar, Ganguly etc. But if the same results in their downfall (as is so often the case) then it is one of the most ugly dismissals in cricket