No it's not the volume of people, it is the number of watts being pulled, a household of 10 people can use less electricity than a household of 4 people, again, it's a matter of scale and lifestyle.
Another example, a family of two parents and 3 children in a two roomed shack has their permanently on 2000W hotplate, they are sitting there keeping warm around it. The place is too small, not everyone can have their own individual hotplate, so they make do with the 2000W.
In a larney suburb somewhere, same sized family, the teenage daughter has locked herself in their bedroom and don't want to be bothered, with a 2000W heater to keep warm. The mom is working in the study, another 2000W heater, the two young ones are in their room, let's be frugal this time, a 600W wall heater is keeping the place warm. Finally the dad is watching TV, a 1000W fan heater.
Do you see what I am getting at?