Every cryptocurrency comes with their own characteristics, so the maximum supply of bitcoins is about 20 million and that is what makes the price of bitcoins to be valuable as it is today.
A difficult question but in my opinion I think the lesser the total supply the higher the price of the coins. Bitcoin price is higher because it total supply is not much compared to other coins
Maybe 21 was Nakamoto's favorite numbers. LOL
Well, if there were 200 million or even one billion supply, we would skill ask the same question, why 200 million, why one billion supply?
The need for it is very important , because inorder to actually make inflation not to affect the coin ,and cause unlimited supply ,it's good to make it scarce to help the price grow
It would be up to Nikamoto to really explained the reason for that,but i think it could just be a way to aviod a situation where the coin will just be every where thereby lossing its value.