The NOTAMs for a commercial flight from JFK to LAX, for example, would be several pages long. Warnings about construction work at either airport, closed taxiways, cranes in the vicinity of the airport, enroute navigational aids which are unusable, etc. ATC can't relay that for every departing flight. Additionally, the NOTAM system is where they'd retrieve these from, so if that's down they have nothing to relay.