A combination of people demanding more detail and designers wanting to show off more, that extra 3 or 4 mil makes quite a lot of difference in figure quality but hardly any in playing space (frontage) on the table. Just compare Minifigs to Gripping Beast etc.
Rick

My Late Republican Romans (some call them Marian or Caesarian) have mainly bronze helmets with some iron, the closer you get to the early empire the more iron ones there would have been. In reality it wasn't a fashion show and they weren't as uniform as today, if it was functional but 100 years old ...

I got in trouble for saying this at Warlords stand at Partizan, but all quick shade really is, wait for it, its furniture varnish!!. Go to B+Q, Focus etc and theres tins of the stuff, I pay about £4 a tin and it ranges from clear (matt, satin or gloss) to very dark (good for brown horses) medium pin...