On observing the flame i discussed with my mother
  the reasons are:
# Using low flame the fuel consumption(LPG) is very less,
using high flame consumes all the fuel fast.
#Keeping the flame controlled and low gives good taste to the food,because 
the food gets overcooked and spoils it.
#using high flame is also dangerous.
#Using also reduces the amount in monthly bill for the gas (LPG)
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While cooking food my mo uses the both low and high flame it because of many reasons like :
1. to ensure that food is not over cooked.

2. To even know that we are not wasting the fuel more and more.

3. To even see that to LPG gas will not be wasted a lot for only one time cooking.

4. We know that the prices of all the fuels have been increasing, so to get rid of this inflation also cooking on high or low flame method is obtained.
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