Once again a bit of education for the non professionals out here :
We ATC do not need POB and FOB, the fire fighters are. We ask because they need to know to help the emergency in the best possible way. One reason among others is the fact that they do no send the same number of ambulances and fire foam trucks for, say a 747 cargo with 2 POB and 100+ tons of Fuel, than you will for an Embraer with 100 pax and 4 tons fuel.
We need this info quickly . As pointed before, not everyone has a ground ops and we ATC do not have all airlines flying out there ground ops contact details , only the major at your hub, and even then, will take too long before you get the right guy at the end of the phone anyway.
The procedure is a a well rehearsed one, standardised by ICAO, applicable globally. Again a standard quick answer in standard phraseology is what will work best and save the most lives in the end.