This just got me thinking: why do they have separate tricorders and communicators? Back in the days of TOS, and even TNG and the other 24th century series the technology wasn't around, but think about it now - with the rate of integration real world technology is going through, don't you think the tricorder/communicator separation thing is going to look a bit dated soon?
If I'd been making the new Trek film, it is one thing I might have paid attention to. Of course, I think I probably would have gotten quite a negative reaction for doing away with the classic tricorder/communicator combo, but it would have made sense given modern technology.
Far from it.
You're looking at this from the standpoint of modern, infrastructure-heavy situations, and mainly from the standpoint of control interfaces, I suspect.
The thing to realize is that the control interface... whether for a contemporary cell phone, or a ST communicator, or a ST tricorder, is a small part of the device.
In the case of a modern cell phone, you're talking about a device which has a tiny, low-power energy storage device, a very low power tranceiver, and a relatively large percentage of the total device dedicated to interface.
Sure, you can play "space invaders" on it, or whatever... but it's only useful as a communications device if you have an active "cellular network" to tie into, so that your teensie little transceiver and weensy little battery pack don't have to do very much.
Now, a Star Trek communicator has a simple user interface, along with a massive power cell and multiple tranceiver sets (at a mimimum, radio-frequency and subspace)... and realize that unlike a cell phone which only has to transmit and receive over a very short distance, this has to be able to reach tremendous distances without the benefit of a compatible infrastructure to collect, boost, recode and retransmit the signal, etc (as cell phones have). It has to work on its own.. meaning it has to produce extremely powerful signals... and collect extremely faint signals effectively. Think more of the communication stations used to stay in contact with contemporary space missions, rather than your pocket cell phone, and you'll have a better sense of what this device does.
A tricorder, on the other hand... has a more complicated user interface, a number of powerful sensor and scanner devices, and a massive-output power cell, along with massive data storage and computing power (by contemporary standards).
Are these REALLY the same device, or remotely the same device? The only thing that they might have "in common" would be the user interface. Functionally, they are not only totally different, but would likely be highly incompatible. Would having an orbital-range transmitter operating next to, and simultaneously with, your super-sensitive electromagnetic-resonance sensing system really be a good idea?
Don't think of it as a "magic box with controls." Think of it as a set of functions. If the functions aren't the same (and moreover, if they're potentially incompatible), well... the conclusion ought to be obvious.