If the number of bitcoins exceeds 21 million, it is no longer referred to as bitcoin. If the limit is changed, there will almost certainly be a fork in the blockchain, resulting in two versions of bitcoin - one adhering to the 21 million limit and the other considered an altcoin. Because of this potential consequence, it is impossible to change the limit.
Those who claim that the 21 million bitcoin limit can be easily changed through software are mistaken about how the limit is implemented. The limit is not explicitly defined in the code, and there is no mechanism in place to halt bitcoin issuance if it is exceeded. Instead, bitcoin issuance is analogous to a car that accelerates quickly before gradually slowing down by applying the brakes. Every four years, the brake is applied more forcefully, resulting in a 50% reduction in issuance. This gradual slowdown is how the 21 million bitcoin limit is reached.
To help explain, consider a similar comparison. Assume you have 21 miles to travel and are halfway there, at 10.5 miles. You begin reducing your speed by half at this point, and then again at the halfway point of each subsequent distance. As a result, your speed continues to slow, similar to Zeno's paradox. Similarly, the 21 million bitcoin limit is achieved by gradually slowing the issuance of new coins. By the time we reach this point, we've been slamming on the brakes for years, if not decades. If we stop reducing the speed (i.e., stop the halving process) and continue at the same rate, we'll only be adding a few satoshis to the total every block, say 10 or 20. It will take a very long time to issue even one bitcoin at this rate. As a result, removing the limit on bitcoin issuance is not a viable option.
Finally, the 21 million cap on bitcoin issuance is a fundamental feature of the cryptocurrency that cannot be changed without risking a blockchain fork. The limit is reached by gradually slowing the issuance of new coins through a four-year halving process. This is analogous to a car applying its brakes to gradually slow down. Removing the cap is not an option because it would result in an infinite and unsustainable supply of new coins, eventually rendering bitcoin unrecognisable. The limitation on the number of bitcoins is critical for the long-term integrity and value of the cryptocurrency.
Source:
aantonop, 2022, "Will There Be More Than 21 Million Bitcoin?",
