Why should you stretch? After workouts it is easy to get lazy or hungry and forget to do it. But here's why stretching is beneficial!
1) Stretching will relax tight muscles and reduce the acid that builds in your muscles (which is the cause for the soreness).
2) How does stretching help with form? Well, if you are more flexible you can get into the correct positioning to perform movements better than someone who can not get in the same position. For example, if you cannot perform a squat due to flexibility, someone who can perform the full squat will see more results because they can achieve a greater range of motion.
3) If your muscles are tight, they are likely putting you in poor posture. As they get tight, they shorten in length. For example, if you have tight chest muscles, it is hard to bring your shoulders back and stand upright. Stretching the tight chest will lead to better posture over time.