Restoring the temple peaks compared to the hairline (photo)

Is there a reason that a majority of hair transplant before and afters the guys dont have perfect hairlines (like the picture)?Like, I want to try and get a perfect hairline.. is there something preventing that? Also, can hair be transplanted as low as you want or will it not grow in certain spots? These are decisions that a patient must make when planning the hair transplant with a good surgeon.

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