Satoshi limited Bitcoin to a maximum of 21 million because good and sound money must have a limited supply , you can’t just print it endlessly.

In the first block called the Genesis Block  Satoshi included a famous message
The Times 03/Jan/2009 Chancellor on brink of second bailout for banks.
This message is a headline from the British newspaper The Times on that day. With it, Satoshi symbolically showed why Bitcoin was created: as a response to endless money printing. Money printing causes inflation
Releasing money into circulation in this way causes inflation, which is most easily described as a decrease in purchasing power. Everyone understands and feels it firsthand 100 usd today buys much less than the same 100 usd  could buy a year ago. That’s inflation, or a hidden tax that we all pay together. But we pay it with money we have to earn, while banksters pay it with money they create whenever they need it

 21 million limit can’t be changed because doing so would destroy Bitcoin and its purpose as a sound and hard form of money The node runners wouldn’t allow that either.If that happened, the invention of Bitcoin would become completely meaningless.