Hair extensions are manufactured hair that goes through a rigorous chemical process that changes the amount of energy on the surface of the hair.
Every surface has a measurement of energy and every liquid has a measurement of tension based on ions.
Since the surface energy has changed, the surface tension in products needs to be changed to properly affect this specific type of hair.
If the balance of the product is not right for the hair extensions, the product will either slide off without affecting the hair or bond too strongly creating build up.
Since human hair and/or hair extensions have a negative charge, manufacturers design their shampoos to have a negative charge, so that shampoo will not adhere and absorb into the hair (because like charges repel and opposite charges attract!)
Conditioners are designed to have a positive charge so that it will adhere with the negatively charged surface of the hair without leaving deposits.