Because, in my experience, you cannot debug anything more than one step removed from the command line; and if you cannot debug then you cannot program. If you are unable to compile, link, and run your code from the command line then you will not be able to fix it when something goes wrong on a system with a slight difference from your dev setup; and they all have slight differences from your dev setup.
Could you say more about why this is important for beginning programmers?
Because, in my experience, you cannot debug anything more than one step removed from the command line; and if you cannot debug then you cannot program. If you are unable to compile, link, and run your code from the command line then you will not be able to fix it when something goes wrong on a system with a slight difference from your dev setup; and they all have slight differences from your dev setup.