Credit Score Understanding

Question: Why don't free credit reports give you your Credit Score?
I've gone to get my Credit Report online through experian but its telling me I have to pay for the actual score. I don't understand why.
Answer: if you are looking for the free Credit Report and score national site, check out this site
http://free-credit-report-national-usa.blogspot.com/
Here you can see your 3-in-1 Report from all three credit reporting agencies and your Credit Score.
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