Pulling on a muscle for a long time doesn't make it longer, doesn't make it more pliable, and doesn't improve athletic performance. There's lots of scientific literature that shows that stretching before exercise increases the risk of injury, but still there's a lot of emphasis on it in common fitness literature. It's similar to the demonization of saturated fats: once a meme gets firmly implanted in the culture, it's hard to eradicate it.
I wanted to share this video from Evan Oscer on why conventional stretching is bad. I think it's worth your time to watch: