PPC Broad match Keywords, Why?

I have found with all my PPC adverts on adwords and bing ads, that the "broad terms" for keywords although always gives me a lot of traffic they never give me sales.. it makes me think is this the case with everyone? or am I just doing something wrong?

At the moment I'm a bit unsure why they offer this.

Broad match is a big money waster. If you want to increase your sales and conversion rate, use exact match and phrase match. Also, use the tools provided to exclude some useless keywords from the search terms you want your ad to show up for, such as keywords containing the word "free".