My thoughts are that this is something only a small fraction of scanner listens would be truly interested in. By "truly interested" I mean willing to put the time in to building and maintaining such a list as well as using it.
Then there is the challenge with getting the actual information. Some times radios move around from person to person. Or sometimes Officer A may be in squad car 1 with Radio ID 1 and the next next day in squad car 2 with Radio ID 2, but his call sign is 1 Adam 12 both days.
Probably many more interested than you'd expect, but it requires the three P's..pen/paper/patience. Many departments have a "pattern" of how the radio ID's are programmed. An example is Illinois State Police, that use the 4 numeric badge/star number which is incorporated into the radio ID at the end. Some Troops, the probationary trooper will receive a call sign corresponding to the ones they use for probationary troopers, and once the probationary time is done, they receive an assigned call sign which I update. The mobiles use the 100xxxx/200xxxx/300xxxx prefix, depending on the zone, while the portables use the 110xxxx/210xxxx/310xxxx prefix for portables. My current list is over 4,000 radio ID's and 99% accurate. I have a field on all my scanners to display Unit ID/with name. It's kind of interesting to watch how some progress from probationary to command staff via the radio ID's.
Other police departments have mobiles that are assigned to the cars, portables aren't assigned but you can assign them a number.
Fire departments are easier, and the fire apparatus have assigned radios and can easily be documented, and the portables can be figured out from there. They normally fall into a "pattern" too, so easy to program if the time is dedicated.
I don't submit the info to the Wiki because it's a pain to manually enter all the information using the format. If it was made available via database download, it would probably be very popular. But...I don't want to be the only one doing all the work while everyone else sits on the sidelines.