What is your reason for offloading capability into a fighter instead of fitting the mothership with it?
Some I can think of:
- parasite is much slower than the mothership (engineless?) and needs to be carried where it's useful
- parasite is fast at the expense for fuel efficiency, and needs a mothership for adequate strategic range
- parasite can rely on its small sensor footprint to fulfil some missions undetected but needs support in others
- parasite carries very pricey equipment that is protected from breakdowns when not in use (or can be used from a hangar)
- parasite carries equipment that naturally lends itself to parasites, e.g. box launchers or fighter-only fire controls
- parasite has very different mission life (days for high-performance craft, years for some early warning assets or "reusable minefield" missile pods)
If there isn't a specific reason, you essentially pay extra for nothing. I suppose there's exposing a less valuable ship to harm, but that doesn't strike me as enough.