Lots of switches were certainly wired that way in the past. My house, which was built in 1964, has the neutral going to all the switches. And that is that standard way of doing it where I live today. Makes it handy when retrofitting switches with electronics that require the neutral.
Interesting discussion, as I've not opened a code book in some time. Lets clarify some things; The standard of only taking the hot and switched leg down to the switch doesn't only date back to the '64 era. If there's been change in this regard, it's a relatively new change. Also, if there's been a change made I wish one of you claiming this would provide a link to it. There are standard practices that vary around the country, that why the NEC is the ultimate reference. The NEC is a minimum however. Additionally, in my experience, I didn't think the NEC made changes to enable things handy for retro-fitting. Dimming has been around for decades and I'm not sure it's any more more prevalent now than it's been in years past.
The effect on induction heating is probably not significant in a typical residential lighting circuit.
Regardless of significance, parasitic magnetic heating is never allowed in any situation I know of.
Grounded conductor (neutral) is not just a voltage reference. It carries full current in a normal branch circuit. In a multi-wire branch circuit, it may carry less, even close to zero, if the load is evenly balanced between the two hots.
I'm intimately aware of the function of each conductor, neutral or otherwise. I've never heard of taking the neutral to the switch, unless the switch needed the neutral for a difference of potential.
In any case, the cost difference between wiring a switch with and without neutral usually isn't much...
I'm not so sure about this. It's entirely different when a third insulated
wire needs to be taken to the switch. I have zero residential experience, however I do know that in that non-conduit environment, 12/2 w/ground is abundant. Most likely 95% of what is purchased and used is 12/2 w ground,...either Romex or maybe even MC. There are some jurisdictions that require conduit for residential, but for this discussion, insignificant.
Anyway, to get a more expensive 12/3 w/ground, changes everything. If conduit and THHN were being used, it would be relatively insignificant. However with 12/2 w/ground, one feeds the switch with the white, the return switch leg is the black, and the neutral is kept up in the fixture JB. As far as I know, this was the standard in the 60s, 70s, 80s, and 90s. If this has changed, and the neutral shall be required in the switch box,...whether the device needs it or not,..it is news to me. I do not follow code changes, and if this is the case, please link to further information.
There are a few instances when the NEC makes provisions to "make it easier on the next guy
", and that's entirely possible here, but it's not likely for reduction of parasitic magnetic heating.
Thanks, good discussion.