I've been thinking about the differences between the 3 types of Stargates: Milky Way, Pegasus, and the SGU gates. The SGU gates are the earliest, and they have some limitations compared to the later gates. For example, a limited range. The Milky Way gates were built second, and lastly the Pegasus gates. But both the SGU gates and the Pegasus gates support remote dialing, with SGU even having a directory of gates in range on their remote dialing tablets. It seems bizarre that when designing the second model of gates, the Milky Way gates, that the Ancients would remove such a useful feature. Has there been any indication of why this choice was made?
Actually every DHD is a remote dialer, just a very large and durable one. There are no physical connections between a DHD and a stargate, they just need to be in close enough proximity for the DHD to communicate and transmit power. The reasons they are large, heavy, pedestals instead of portable devices are:
- They don't want them to get lost, you don't want some primitive species to misplace it (Looking at you Tau'ri)
- They need to be able to produce power to the gate for multiple millennia without recharge or refueling.
- They need to be nearly as durable as the gate.
The Puddle Jumpers are equipped with remote dialing devices, and in Moebius we see it working on Milky Way gates. Also there are indications that the Goa'uld may have portable dialing devices. In SG1 "Children of the Gods", Apophis is able to dial out from the SGC even though the facilities had been mothballed, one would assume mothballing included cutting off the gate's power. Later in the series Hammond rants to O'Neill about "How expensive it is to dial that thing" when there is talk of the SGC being shut down. It is also possible the Needle Threader from SG1 "Into the Fire" is equipped with such a device even though it is not called out.
The obvious answer to this is that the writers didn't come up with the idea of remote dialing until making Atlantis and Universe, and that's why it isn't in SG1.
However, I think there is some in-universe support for why we only see the pedestal style DHD devices throughout the Milky Way.
The vast majority of the Milky Way gates were located on planets where the population was very technologically limited, to the point where things like computers were far beyond their capabilities. For these sort of people, a computerized, portable dialing device seems far less practical and usable than the simple interface on the DHD. Additionally, we know that other interfaces with the Milky Way stargates are possible, as evidenced by the dialing computer in the SGC or the pedestal that dials the gate when Daniel is attempting to help build Merlin's weapon. This would indicate that it's entirely possible that the Ancients had some sort of portable device that could dial the gates.
Short answer is that remote dialing is certainly possible, but the Ancients didn't leave any remote DHD devices just lying around.
Advances in technology made remote dialers obsolete.
You mentioned the remote dialers' use as a database:
...with SGU even having a directory of gates in range on their remote dialing tablets.
The repository of knowledge made gate directory devices redundant, since any Ancient could quickly download the entire gate directory directly into his or her brain, as O'Neill did in "The Fifth Race". Destiny-era neural interfaces were cumbersome, which may have made them unsafe or unpopular for such use.
In tandem with the ubiquity of ground- and ship-mounted dialing devices, the elimination of the need for gate directories would have made handheld remote dialers obsolete for most uses.
They have lost DHD's and whole stargates. It's entirely possible that they had tablet like devices that held all the addresses in the network. The earlier SGU gates uses tablets that held all of the gates in range, plus controlled kinos. So it only makes sense that a tablet in the Milky Way would have a list of all of the gates in range (AKA All MW gates) and probably info on the planets and any other features they might find useful. There a Technologically advanced race...There going to have some kind of tech with them.