While businesses which pay for their employees' tickets all want lower prices, the ULCC's don't attract much of that vast segment because of a lack of interline ticketing, baggage, and IRROPS services. Put simply, all it takes is having an employee stuck somewhere he should not be and having to purchase a full fare ticket for him to get home because the ticketed ULCC lacks backup aircraft and crews.
It is not about whether the stale sandwich is included in the ticket or not, but whether the cheaper ticket winds up being more expensive in the end.
The model will only work when consumers accept that you get what you pay for. FI has done that quite well.