I like to imagine the situation of a tax collector in ancient Mesopotamia, going around and asking the farmers how many animals they have.

If the farmer has 5 cows, they have a number of cows that you can put in a form on a clay tablet.

If the farmer has no goats, they don't have "a number of goats", they have no goats to count. Writing a number on the tax form doesn't make sense.

If numbers are only used to count actual things in the real world, zero is a very odd concept.

We realized later that having "a number" to represent "none" simplifies many things and rids us having to deal with special cases. And if we teach it to children early enough it isn't too confusing.