The hamstrings get a lot of criticism for being too short and tight. Every time we walk ,run or bend over to pick something up we stretch our hamstrings . Time spent on stretching the hip flexors and mobilising our thoracic spine would be more beneficial .
We are a flexion dominant society so on a basic human movement level it stands to reason that we shorten our anterior chain and lengthen our posterior chain just from our every day posture and activities.
I have to bite my tounge here and resist the urge to go on a rant about how people need to stop stretching their lower backs because they are already overstretched from poor posture and too much flexion.
I do believe that the hamstrings in their role as synergists to the Glutes ,decelerators and force transmitters between their attachment points on the pelvis and lower leg as well as pelvic stabilisers work hard and need to be stretched .Before this important process though they need to be softened and deinervated.