12 AWG for lights IMO is overkill in most residential homes ... if anything the power needed for lighting has been going down. For years 14 AWG was used when most all residential lighting was incandescent. Then most switched to CFL (which consumed much less). Now most residential lighting is heading to LED. So, lighting is using something between a 5th to a 10th of what it used to. Some numbers off the top of my head ...
an efficient non-dimming led light can give you around 100 lumens/watt,
a dimming one a bit over 82-85 lumens/watt
an incandescent about 11 to maybe 15 lumens/watt.
Now all that said some people still insist on only putting in incandescent ...
