broad match

Why do people recommend that you use "exact match" numbers from Google Keyword Research tool? Why are "broad match" results not good? Aren't most of the people how search for your keyword not going to use quotes? i.e. aren't most of the searches going to be broad searches?

Hey all, long time no talk. My first q is this: What's the difference between "cocacola" and cocacola with no quotes? Will Google consider cocacola a broad match phrase and search similar things like 'soda' or coke' etc.? or is one word going to be exact match. I just need some advice for...