Because quite simply, you are too bald and too young to be a suitable candidate for a surgery. Hair transplantation isn't for everyone, and it would be a damn shame if you invested money, emotion, and time in a procedure that ultimately will leave you dissatisfied. I have never seen a person with your degree of loss have anything close to a satisfactory result for a person in his 20's. The only time a person with your degree of hair loss should even consider a surgery is if that person is willing to rock an ultra conservative frontal forelock pattern. Sadly, that would look ridiculous on anyone under the age of 50, at the absolute youngest.
If you decide to proceed with Dr. Umar I wish you nothing but the best, but I would see if Dr. Umar is willing to guarantee survival and growth of the body hair.