Stretching occupies a strange position. Almost everybody agrees it is good, almost nobody can say precisely what it does, and the research has spent thirty years quietly contradicting several things people were taught in school. It is worth going through what is reasonably well supported and what is not.
It probably does not prevent injury
This is the claim most people would put first, and it is the one on the weakest ground. Reviews of static stretching before exercise have repeatedly failed to find a meaningful reduction in injury rates. The idea persists largely because it was taught confidently for decades, not because the evidence caught up with it.
Warming up does appear to matter. But warming up and stretching are not the same activity, and the benefit seems to attach to raising tissue temperature and gradually increasing intensity rather than to holding positions.
It probably does not prevent soreness either
The muscle soreness that arrives a day or two after unfamiliar exercise has been studied specifically in relation to stretching. The effect, where one is found at all, is small enough to be practically irrelevant.
What it does do
Stretching increases range of motion. This is not in serious dispute, and it happens fairly reliably with regular practice. What is more interesting is why, because the traditional explanation has not held up well.
The intuitive picture is that muscle lengthens like elastic being permanently stretched. Current evidence points somewhere else: a substantial part of the improvement appears to come from increased tolerance to the sensation of stretch. In other words, the tissue has not necessarily changed as much as the nervous system's willingness to allow the position has.
Range of motion improves. The mechanism is less about lengthening tissue and more about the nervous system permitting a position it previously resisted.
Timing seems to matter
Long static stretches immediately before an activity requiring power or speed have been associated with a temporary reduction in force production. The effect is modest and probably irrelevant to most people going for a walk, but it is the reason many coaches moved pre-activity work towards dynamic movement and left longer holds for afterwards or for separate sessions.
Form matters more than depth
The illustration above shows the distinction that causes the most confusion. Reaching towards your toes can be done by hinging at the hips or by rounding the lower back. They look similar from a distance and they load quite different structures.
Going deeper into a stretch is not the goal. Reaching a position where you feel mild tension, and staying there calmly, is enough for the range-of-motion effect described above.
So is it worth doing
Yes, provided you want what it actually offers. If your reason is that you want to be able to move through a fuller range comfortably, the evidence supports you. If your reason is that you have been told it prevents injury and soreness, it is worth knowing that this is not well supported, so that you can decide whether you still want to spend the time.
Twenty to thirty seconds per position, a few times a week, is the range that appears in most practical recommendations. Longer holds do not appear to add much.