[returningfory2]

There's one small part of the article that IMO is sort of key to understanding the why:

> [for every account] we keep two separate strictly positive integer amounts: one for debits and another for credits

It is not sufficient that their integer type is able to handle individual transactions. Their integer type must be able to handle the sum of the absolute value of all transactions that have occurred on an account. And I think it's easy to come up with realistic situations where you hit that.

So say you take the NYSE, which trades about ~$18 billion per day [0]. This is ~$1.8 trillion cents, or about 2^51 microcents. After 2^12 business days (~=16 years) you'll already be hitting the limit. (This is just a toy example ofc.)

[0] https://www.nyse.com/trading-data#:~:text=The%20New%20York%2....