But the idea is not that you as the end programmer "make optimal use of a computer's memory hierarchy".
It's that you write in a way that makes it easy for the runtime to ensure what you do is solid and correct and scalable -- and it's up for the runtime makers to make sure it makes optimal use of the computer's memory hierarchy.
And it's also that you sacrifice some of that "optimal use", to get the "solid and correct and scalable" part.
Apparently more easily, with a faster time to market, and with less errors than alternative languages. E.g:
https://blog.discordapp.com/scaling-elixir-f9b8e1e7c29b
https://www.wired.com/2015/09/whatsapp-serves-900-million-us...
But the idea is not that you as the end programmer "make optimal use of a computer's memory hierarchy".
It's that you write in a way that makes it easy for the runtime to ensure what you do is solid and correct and scalable -- and it's up for the runtime makers to make sure it makes optimal use of the computer's memory hierarchy.
And it's also that you sacrifice some of that "optimal use", to get the "solid and correct and scalable" part.