At first glance, there is nothing special about the periodic halving of releases. But if you do some math, you can easily see that if the time of each period is equal, when the first halving happened, it represents there are nearly 50% token in circulation of the max supply, and when the second halving happened, the circulation is nearly 75% of the amount. This has nothing to do with the total number of tokens, the output of each block, or the duration of each halving cycle, but all halving models with equal cycles follow this pattern. To put it bluntly, if all token of a project are diluted through liquidity mining within 4 years, and halved each year, then half of the total tokens will already be in circulation by the time of the first halving occurs. This is not a small amount, after all, many teams account for 10% of the max supply, and there is a lock-up, often not fully released until the end of mining.