The maximum frequency for the DCC signal is a little under 10 khz, with an average usually around 7-8 khz, which puts the skin depth for copper wire a little over 0.025 in., so it has practically no effect on 16 gauge wire or smaller. There are two main reasons for the emphasis on wiring when it comes to DCC. The first is voltage drop when you have several locos or consists running off of one power supply. As an example, let's say you have a double track mainline running by a yard, and you have a loco working the yard and two trains passing by on the mainline at the same time. In DC, you would have to have separate blocks with separate power supplies each feeding the block they are controlling with a set of wires. Each loco or consist is running off its own set of wires which can be done with relatively small gauge wire. With DCC, all of these locos will be running off of one power supply (unless you have it divided into booster districts) - if you are feeding the area with one set of wires they are likely going to need to be a larger gauge than what was required for DC to prevent too much voltage drop. The other main reason is for protection against short circuits. With DC, it generally does not take as much current to trip the circuit breaker in the power pack (if it has one) and, in my opinion more critical, you pretty much know if you have a short - one train, one power pack, if the train you are running causes a short, it stops, and you generally know about it right away. With DCC, it generally takes a lot more current to trip the circuit breaker - a short that draws 1.5 amps may trip the circuit breaker on a DC power pack, but won't in a 5 amp DCC system. Poor wiring causes extra resistance which decreases the amount of current a short will draw. You can actually have a short occur in one area and still be able to run trains elsewhere, and that short can be drawing quite a bit of current, possibly melting something. On smaller home layouts, these two issues are not nearly as critical as they are on large "club size" layouts. Many people seem to think the emphasis on wiring has to do with making sure the signal gets to the loco, but that simply isn't the case. With the signal being the full amplitude of the power, if the loco is getting power, it's getting the signal. Well, one of the biggest complaints about DCC is still that it is more expensive than DC, add wireless and batteries to all of the locomotives and that will only get to be more so. Even if it didn't, I still would have no desire to have batteries in my locos.