Thin CA is not 'necessary' but you already have 2 reasons to have it around (hinges and screwholes). It's also useful to harden balsa (after poking a few pinholes) tack gluing, for securing thread windings used on some vintage kits and can be useful during the application of balsa sheeting to wing or fuselage framesand for lining ABS cowls with light fiberglass cloth. With a good applicator tip it can be controlled. I don't use much of it but always have it available. Of course if you're allergic to it, use something else.