I work at Motorola Solutions, the company who makes communication equipment for the military, police forces, fire fighters, businesses, etc.
I recalled the hype around the office over going digital for TVs, the abandoned UHF and VHF frequency bands would be opened up for communication purposes. I am not sure that was the primary reason or just the resulting benefit to our industry. After 9/11 lots of things got changed up to help with national security, and maybe this was one area of change for that reason.
I strongly lean toward the reason to go digital was primarily done for consumer entertainment benefit and growth of the economy. The opening up of those frequencies for 2-way communication was right behind it. A win/win except for a select few people like me and dodge_guy where our reception at home suffered.