Stretching is not an important part of fitness. Its primary goal — flexibility — does not correlate. And it’s also easily achieved with other kinds of exercise that are much more beneficial for fitness in other ways. Most stretching is simply a waste of time.
Stretching just doesn’t have the effects that most people hope it does. Plentiful research has shown that it doesn’t warm you up, prevent soreness or injury, contribute meaningfully to rehab, enhance performance, or physically change muscles. It may boost flexibility, but the value of more flexibility is unclear, and no other measurable and significant benefit to stretching has ever been proven. Regardless of efficacy, stretching is inefficient, “proper” technique is controversial at best, and many key muscles are actually biomechanically impossible to stretch — like most of the quadriceps group.
To some extent, the controversial thesis is put forward by Paul Ingraham in PainScience.com and supported by the Sports Medicine article.