Stunning that cities as large as Dallas haven’t wised up and encrypted their radios.
Its extremely expensive. They probably have at least one channel encrypted, but encrypting everything, very expensive.
Not to mention, police radios getting lost is a regular occurrence. A fully encrypted network would require the re-encrypting of every radio out there.
Generally, encrypted channels are configured on any digital public service system but are only used when justified. Using them exclusively would invite legal challenges.