How many people will have a whole bitcoin? How many bitcoin…

How many people will have a whole bitcoin?
How many bitcoin do you need?
We throw bitcoin around like its a second hand pair of shoes right now, in the future it may buy businesses or small cities! Without buying @Gopnikz now it wouldn't grow into the market we dream of tomorrow.

So, if there are 21 million ever and 7.5 billion humans.
Is 1 enough?
Do you need 10 or 50 or 100?
Do you have obligations to start businesses if you have a 1000?
Should you feel the need give some to charity if you have over 1000?

Thoughts and responses expected and welcome.