Thanks for the tag @kdjohn.
Short answer: No, stretching is not necessary and it doesn’t prevent injury.
Does it still have applications? Yes it does.
First of all, anyone who claims to know how stretching exactly works (without a doubt) is lying as it hasn’t been proven yet.
The theory I find most convincing and to my knowledge, that the reaserch field is leaning towards is that stretching increases stretch tolerance (desensitization and increased pain tolerance).
The length of a muscle has nothing to do with tightness (exceptions include post op cases), it’s the nervous system that “creates” tightness as a protection mechanism to prevent the body from taking damage or because a certain structure within the system is not strong enough to do what is asked of it (as stated above already). So you don’t experience pain because of your posture or because a muscle is tight, you have a certain posture or tightness because you’re in pain and the nervous system limits range of motion of nearby structures because it detected a potential tissue damage.
Research has shown that stretching has no effect on injury prevention.
Research has shown that strength training is at least as effective to increase range of motion as stretching and mobility training.
Research has shown a potentially positive effect on cardiovascular health by stretching.
Agreed. Stuff like “you’re hip flexors are tight because you sit all day” is still WAY to commonly thrown around.
The human body is not a machine and shouldn’t be explained like one, using reductionist models.