I was thinking why is it only 21 millions and there are more or less 16 millions left to be mined? Why don't we have an unlimited supply so everyone including myself can mine atleast 1BTC in the future? Reading your comment made me realize that this is a market, the law of supply and demand still applies. There should always be a limit and difficulty in having one btc so that its value goes up.
If you add more coins to BTC, there will be a higher supply of BTC and each of the BTC will drop in value. That is obviously not what anyone wants and everyone is likely going to oppose it.