Why fire happened when there is sufficiently fire fighting men & machines are present?

Men and machines reactive measure after happening to minimize losses. Proactive measures required to prevent fire. 

 Yes , I agree that the question is simple . so simply the answer is that the above mentioned fire precuation as well as insurance are not prevent the incident of fire to be occurred , ( BUT THEY ARE ONlY MINIMIZE  RISK AND  LOSS ).

In other words if all fire precuations accurately installed and be in an opreational conditions does not pervent the occurrence of fire incident , but definity minimize the loss.

Regards.

this is due to lack of mitigation or peventive measures which can reduse the risks of such incidences.this can be done through awareness adn education

Lack of resources,procedures wrong method statement lack of risk assessment and job hazards analysis ...  only sufficiently fire fighting men & machines cannot grant you a safe environment unless safety /precautionary measures no take in place  

Watch this ....Fire Fighting Webinar...i think its help full.

https://www.youtube.com/watch?v=5x0Tz-1zSOw&index=1&list=PLgwFrn4WS09Fx2-3l2xD55eLFmyVREVLe&t=1s

Fire fighting men & machines are no matched if the fire is consuming large quantity of flammables and explosive materials.

To have a really great system you need to have a another pair of eyes. It' the best to be professionals and you and your family will be in a great mood. That is my opinion but if you find some other solution that is more better for you. Regards from me.