I am really confused about collective nouns. I get the fact that many collective nouns like team, family, army can be used in both singular and plural forms (teams, families, armies) and can be used with numbers like 1 family, 2 teams etc. whereas some collective nouns like police, cattle, staff, personnel, people etc. are always plural.
But my confusion is that even if they are only plural, sometimes we do use them with numbers like 15 people but sometimes we don't use them with numbers. I haven't seen someone saying "3 police were there". If nouns like police, staff, etc. are truly plural, why don't we use them with numbers?
If we don't use them with numbers, shouldn't they be placed in a separate category of "uncountable but plural nouns"?