Give three benefits of doing survey of avilable materials?

1) So you have a quota of the materials you have in stock.
Allowing you to know how much of a set group of materials you can export, and inport when you require it.

2) So you don't expend resources you don't already have available.
Much like basic Mathematics and Apples; if you have 3 Apples and give Jimmy 4 Apples, it simply doesn't work.

3) So you don't order in more resources you don't require.
I realise this' simply a repeat of the first point, just rehashed to make it look different. But there's not really a lot more to the question than these 2/3 points.