Building digital radio voice networks with great coverage must account for human psychology, lest the network should go to waste.
Where I live we have a massive linked DMR network that covers not only our state but portions of two neighboring states as well. It is robust. It is a technological achievement. And it is simple to use because its designers made a deliberate choice: one timeslot = one network = one talkgroup.
The wide area talkgroup is on timeslot 1 and that's all that timeslot carries. So you know that when you key up, your voice is being carried with perfect digital replication across dozens of linked repeaters covering tens of thousands of square miles. Everyone who's tuned to that network can and will hear you with perfect digital clarity.
And there's the problem.
I cannot speak for every ham, but personally I do not want to light up the entire state and beyond whenever I want to have a conversation across town. So I avoid the wide network like the flu. It's ingrained in me: don't disturb others unless you have to.
Fair enough: the designers thought of that. The network is also divided into several smaller sub-networks that utilize the other timeslot (timeslot 2). These networks are North, Central, and South. So now you only light up a third of the state when you want to talk across town.
Still a problem?
Even if it's not, here's the issue: I want to talk to somebody one repeater over but that repeater is not in my sub-network. So guess what? I have to use the wide channel and monopolize the entire system for my relatively local conversation.
(…and this says nothing about having to listen to the entire state…)
So there you have it. Perhaps some hams get enjoyment out of broadcasting their voice across as many square miles as possible. But are those hams the same ones who enjoy modern digital modes? Especially when they know the true capabilities of those modes?
The evidence seems to point to “no.”
It's not that the DMR hams are not out there. At least half of the hams I know have a DMR radio of some kind. It's that the infrastructure doesn't work how they want it to. They are keenly aware that their voice is carrying across the entire state. Perhaps they don't want that.
Perhaps – just perhaps – they'd like a little more control over who hears their transmissions. Perhaps they only want to talk to family members. Or to members of their small social club. Or to that one friend who lives across the metro area.
DPCN would give them that choice.