Switch film is used to fill in the gaps between top & bottom housings after the disassembly for the lubing. Since switches are made out of plastic, it is vulnerable for transformation. Therefore, it is advised to use switch film.
Our RND (Research & Development) team researched how to make better switch films.
This design is specifically made so that even if you pull the switch out with the switch puller, the switch film will remain intact (it won't be miss-aligned)