Because Diesel or Petrol is very polluting and smoking gas for environment. It leaves more residues when burns . Also the petrol contains lead (Pb ) which gives a problem in our nervous system and brain . And it catches fire easily and its ignition temperature is very low . Hence we use LPG ( Liquefied petroleum gas or liquid petroleum gas ) as a fuel in stoves . 
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Both of them are very imflammable as they catches fire easily...they both produce many smokes...and their calorific value is they are not used in stoves...
Diesel and petrol both are very dangerous to used as household...