That's not really as necessary. Unless it's a large airport like ORD, JFK, MIA, etc, most cargo operators only have 1-2 flights a day out of an airport, so a major issue leaves them with very little options. Even your normal small- to mid-size airport will have an airline fly multiple flights a day to multiple hub cities, so re-accommodating delayed passengers tends to be easier, and certainly more economical than operating sweep flights every day. Also the sweep flights are really only to cover mechanical issues, as weather delays will affect all flights to/from a particular airport.

If things do get bad I know Delta will operate a "rescue" flight to send an empty plane up to pick up passengers stranded due to a mechanical issue, but again doing that on an as-needed basis is way cheaper than having a flight in the air at all times.