-snip-
We each have a banana. We each cut our banana in to 10 pieces. I then cut each of those pieces in half, giving me 20 pieces. You buy a second banana and cut it in to 10 pieces too, giving you 20 pieces as well. I keep cutting my banana in to smaller and smaller pieces, whereas you keep buying more bananas. Only I have the same amount of banana as we started with, whereas you have increased the total amount of bananas.
Subdividing 21 million bitcoin in to smaller pieces is not the same as raising the cap of 21 million bitcoin, regardless of what units you are considering.
Did Satoshi (and other developers) not consider the impacts of lost coins and population growth?
Sure. Here are some quotes from Satoshi regarding lost coins and population growth:
To Sepp's question, indeed there is nobody to act as central bank or federal reserve to adjust the money supply as the population of users grows. That would have required a trusted party to determine the value, because I don't know a way for software to know the real world value of things. If there was some clever way, or if we wanted to trust someone to actively manage the money supply to peg it to something, the rules could have been programmed for that.
In this sense, it's more typical of a precious metal. Instead of the supply changing to keep the value the same, the supply is predetermined and the value changes. As the number of users grows, the value per coin increases. It has the potential for a positive feedback loop; as users increase, the value goes up, which could attract more users to take advantage of the increasing value.
Lost coins only make everyone else's coins worth slightly more. Think of it as a donation to everyone.