Novice recipe question
I'm a novice bread-maker: I've made three loaves, two with grocery-store yeast, and now I've got my sourdough starter going well and I made one loaf with that. The grocery-store yeast loaves had terrific texture but a bland, uninteresting flavor. The starter loaf was a little on the flat side but had a great crust and the flavor was amazing.
Now that I've got my starter going, it seems like a straightforward way to make bread would be to combine my flour, water, starter, and salt, maybe knead or fold it, let it rise overnight, shape it, and bake.
But that's not the process I see in the recipes I read. Most of them have multiple phases. For example, the starter might be mixed with a fraction of the flour/water and rise overnight, and then more flour and water would be added the next day. And for many there's a "final proof" phase before baking.
I guess my main question is why all the ingredients can't just be combined from the start -- what's the difference?
And secondarily I'm just trying to get a better handle on the purposes of the different phases or processes -- what does each one accomplish?