1. God needed it – He who saw the people grow from a mere 70 souls to a great nation wanted to rejoice at His achievement.
2. Moses and Aaron needed it – they could only care for the people by getting to know each person.
Rav Soloveitchik points out that counting serves two purposes: to know a total (e.g. the amount of money you have, in which case each individual coin or banknote is almost irrelevant) and to savour each separate item because you know that the small things add up to the total. Do one good deed, and it becomes a link in the overall chain of achievement.
Linking this idea with Nachmanides, Rav Soloveitchik wonders how Moses and Aaron could be expected to recognise every single individual.
Before coming to his explanation, let me recall a headmaster I knew, Mr Mackerras of Sydney Grammar School. He had a large boys’ school and he tried to learn the name of every one of his students. If he met a boy whose name he could not remember, he gave the boy a chocolate. The boy enjoyed the chocolate, and the headmaster never made the same mistake twice.
Back to Rav Soloveitchik: he says that when the people sinned, Moses said to God, “They are Your people!” Henceforth, God expected Moses to be able to say, “They are my people!” and to blame himself for anything they did wrong. He could not be a worthy leader unless he knew who everyone was and how each one had to be treated.
Every leader has the same responsibility, which is why, when Rabban Gamliel discovered the poor living conditions of Rabbi Joshua, he deserved a rebuke for being unaware of how a colleague lived (Ber. 28a).