I know in my state - if I offer home prepared food, I will have to have my kitchen licensed as a commercial kitchen. I'm not currently in a position to do that - so I do not offer food that isn't prepackaged in a commerical facility. I would guess that many states/locations have the same requirements and to stay out of the fray, Airbnb will not include a searchable filter option. It would seem to me that if Airbnb officially presents to a guest that food is included, they are ensuring that local laws are being met, and that's not a headache they would want.
On a related note, if I were visiting and saw your listing offered a meal - I WOULD be attracted to that. I'm not personally ultra hung up on licensed kitchens, as I've seen some that were much dirtier than my own or a friends kitchen. So definitely keep it in your listing, I just wouldn't hold my breath on Airbnb making a searchable filter.