Probably because the core DirectConnect system operates on a completely different infrastructure than the phone side and is much more reliable in emergency cases even when the phone-based networks are getting hammered to the point of 'All circuits are busy!'. Ask anyone here who has any Nextel devices and used them in a hurricane or flood or any other major emergency and they'll praise it.
There's also the fact that pretty much all Motorola built Nextel phones have the ability to run as a point-to-point (or phone-to-phone in this case) digital PTT even when there is no network available.
Unlike other cellphone networks, Nextel is actually designed from the ground up much like Motorola's own trunked radio systems. In fact even their own documentation and network schematics refer to tower transceiver equipment as base stations and phones as radios. The air interface acts just like a trunked radio system. And, hilariously enough, the actual interconnect side (normal 10 digital phone calls) is just an afterthought to the system and is mostly just a kludge on top of the radio system. It acts no different than say having a radio at the tower taped to a phone handset and making your call on another radio out in the field.
Put it quite simply: Motorola designed the iDEN system for reliability and availability first and foremost and when Nextel was actually Nextel they took that to heart and that is how it has been run ever since.
The government and various public service/safety groups are not stupid. Nextel has a superior product that works.
This is precisely why I posted earlier pondering what Sprint was going to do with the network. Moreso hoping it actually gets sold off and to someone who is responsible with it. Since Motorola hasn't made a peep at all in regards to thoughts about getting out of the business I have a large assumption they are going to have a lot to say about where Sprint goes with this. -- I swear, some people should have pace-makers installed to free up the resources. Breathing and heart beat taxes their whole system, all of their brain cells wasted on life support.-two bit brains, and the second bit is wasted on parity! ~head_spaz