Luggage. Airlines make quite a bit hauling cargo on passenger flights so they are essentially subsidizing seats as long as people don’t check bags and charging inflated prices when they do.

Convenience especially in terms of number of flights. This gets into a bunch of economic and logistical issues, but airlines are happy to abandon less profitable areas. While regulators want regular service even if the demand isn’t quite there

Service. The minimum number of attendants is based on safety, airlines would happily cut those workers.

Safety.