Another way to analogize: imagine the westward expansion of the USA also being subject to "halvenings" like this. In years 0-9, settlers were encouraged/allowed to settle on 1000 miles worth of land (counting linearly westward), then years 10-19 only 500 miles further, than yes 20-29 only 250 miles further, etc.

Early settlers are incentivized to grab large swathes of land quickly and cheaply, to get the system bootstrapped. Later settlers have to fight over smaller tracts of land, because after all the land is finite (you eventually reach the ocean). However, the land is also nicely divisible into smaller and smaller sub-plots, so units can be adjusted as needed.

The rules by which this "westward expansion" are governed are written into the Bitcoin protocol. But unlike land and the ocean which are natural facts for the most part that we take for granted a priori, with Bitcoin the "border"/limit here is also defined as a theoretical construct (and hence, could theoretically be changed, but this would be a hard fork and people would have to reevaluate the value of a new network with a new set of boundaries/rules).