We squat before we clean. We strict press before we push press. We learn a strict pull-up before a kipping pull up.
The importance of strict pull-ups, or any strict variant of a movement, must be understood before adding the speed or high stability demands that come with kipping. This allows for proper movement mechanics, better skill transfer, and a stronger base of support. Front squats, for example, not only increase lower body and trunk strength, they provide a phenomenal base of support for cleans. If you can show competency in a front squat, you can begin to add the higher speed and stability demands involved in performing the olympic lifts. Conversely, any weakness in a strict or base movement will expose limiting factors that carry over to other movements. If you tend to arch your back in a strict pull up we can see this carry over to excessive arching in deadlifts or squats, which can lead to future dysfunction, pain, or worse. Once you attain a base level of strength and can maintain proper body position you are ready for higher-level skills. Mastering each stage of a progression, and applying proper accessory work, is the key to finding that strength.
To build that strength it’s important to understand what muscles you need to be targeting and what positions your body needs to be in. The primary movers in a pull-up are your latissimus dorsi (lats), trapezius (mid and lower traps in particular), rhomboids and surrounding muscles of the shoulder girdle. Your core muscles play a large role to stabilize and connect the entire body so it moves fluidly and in one piece. Your body position will dictate to what degree these muscle groups are activated. To achieve maximum activation you must have a braced core, neutral head position, and retracted, depressed, and externally rotated shoulder blades (down and back!). Any scaled version of a strict pull-up must allow for this. Using a band for example, allows you to pull your body up in a sub-optimal body position, which has very little, if any, carry over to a strict pull-up. A bar-assisted pull on the other hand, forces you to brace your body and practice proper pulling mechanics all the way through.
Kipping allows you to use hip power to accelerate yourself into a pull-up/toes-to-bar/bar muscle up etc. You kip by rotating through your shoulders into hollow body, and superman positions. Power is an expression of strength meaning, the stronger you are, the more power you can potentially produce. Strength in pull-ups comes from strict variants, and cannot (or to an extremely lesser extent) be gained performing kipping pull-ups. You may be able to get one or two due to strong hips, but your shoulder is at risk of injury due to a lack of shoulder girdle strength, mainly in the eccentric (lowering) portion of the pull-up. It’s like having a high performance car with no brakes: lots of power, but no control. Incorporating kipping drills even without a strict pull up is absolutely okay IF you are only practicing a beat swing, or other skills such as knees-to-elbow or in some cases toes-to-bar. Kipping pull-ups cannot replace strict pull-ups, but kipping drills are recommended for future skill acquisition and performance.
Understanding the importance of strict strength work will only serve to improve your overall fitness and well being. Many limiting factors in other movements could have their roots in the inability to perform these strict movement patterns. Spend time finding what those factors are, put the work in, and see yourself improve in all aspects of your training.