Because VHF/UHF is limited and overloading, assigning frequencies from other pools less used is a vital option.
Same reason, the NTIA is allowing some Statewide systems to be assigned Federal VHF/UHF channels.
As GTR mentioned, many a waiver existed long before it became popular to take from other pools.
In Boston we had the same issues 161.2200 for a Local Ambulance Provider as well
Why are they coordinating AAR (Railroad) Frequencies for non-Railroad use?