The supply of BTC was capped at 21 million in order to have an artificial supply to which its price would increase over time.

This aspect of BTC makes it very desirable either as a short or long-term investment for traders and investors alike. Satoshi envisioned that BTC would be the currency to use in order to eliminate the need for a third-party consensus in handling our transactions. If you also find it somehow difficult to comprehend, I highly suggest watching this video below (link posted below) for an easier explanation regarding the basics and fundamentals of BTC.

LINK: https://www.youtube.com/watch?v=k53LUZxUF50