All products, whether commercial or homemade, can lead to build up on the scalp and strands. Conditioners meant to protect and nourish the hair along with stylizers that aid in holding styles work by coating the hair shaft. As product build up accumulates on the hair shaft it becomes a barrier to any other product used on the hair. In other words it blocks other products from getting through the cuticle. When I had dimethicone build up my hair would not be conditioned or moisturized no matter what product or how generous I was with it. Build up will clog the cuticles, which in return does not allow product in or out. And if you cannot get products like, say, moisture into the hair strands they begin to dry out and will eventually break off. I appreciated the need to clarify my hair after that dimethicone incident (which I got rid of using a clarifying shampoo – dimethicone is one of the stronger cones).
Nowadays I rarely have build up (noticeable at least) I think because I use very minimal products. Bi-weekly muds (in the winter it’s weekly), light conditioner (sometimes) afterwards and finally homemade leave-in conditioner and moisturizer with an occasional oil sealing. Maybe once every 6 weeks, I will deep condition using some type of food (yogurt, eggs, avocado etc) and a teaspoon of the homemade herbal hair oil. Even though I can count on one hand the number of products used on my hair (and I really have no visible problem with build up), I like to clarify my hair just in case.