Functional artificial blood could solve a lot of problems, so why hasn't it been created yet?

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Sources:
https://www.sciencedaily.com/releases/2017/04/170419100831.htm
https://www.statnews.com/2017/02/27/artificial-blood-substitute/
http://www.smithsonianmag.com/smart-news/fake-blood-will-go-clinical-trial-uk-180955721/
http://www.independent.co.uk/life-style/health-and-families/health-news/nhs-to-give-volunteers-synthetic-blood-made-in-a-laboratory-within-two-years-10343279.html#gallery
http://www.nhsbt.nhs.uk/news-and-media/news-articles/news_2015_06_25.asp
https://www.newscientist.com/article/dn27783-what-is-artificial-blood-and-why-is-the-uk-going-to-trial-it/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2738310/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2728196/
http://www.nhsbt.nhs.uk/research-and-development/research-themes/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC137239/
http://www.sciencedirect.com/science/article/pii/S0749070408000845
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3578950/