Mobility is extremely important. Static stretching is not. Dynamic stretching, massage/fascia release, nutrition, and promotion of rapid healing of microinjuries are all very helpful. Mobility work has a large stretching component, but static stretching pre-workout has no known benefits once a dynamic warmup is included.
I can also see how a coach would regard mobility work as something that needs to be taught and then performed on an individual basis by the players on their own time, rather than something that should take away team practice time.