Okay Terra Firma I actually have a decent explanation...there are a few reasons why: first congrats on the contest for your first you did pretty darn well.great job.now I do this for a couple of reasons 1) preference that helps motivate me. let me explain I used do do all the bases etc..but I find when I fully finish sections let's say I do a face all the way through and I like the look of it,this will further inspire me to take extra extra care as I do the rest of the model each section finished I find I'm not so eager just to get that feeling we all get and rush to finish it..so it motivates me to take extra special care with each part plus I love how I see the model come to life after each and every section.
Now COME THE BIG GET REASON...IT KEEP MY MODEL BALANCED; MEAN ING LET SAY I DO THE FACE AS AN EXAMPLE AGAIN...AND ITS A (COULD MODEL MEAN ING LOTS OF COOL TONE SHADES AND HIGH LIGHTS LIKE A YETI) LET SAY I PLAN ED TO PUTTY COOL TONE IN THE FACE....BUT BEING I DONT USE RECIPES I C HORSE COLORS ON THE FLY)NOW AGAIN THE FACE OF THE YETI LET SAY I PLAN TO PAINT THE FUR COOL GREY MEANING THEREs blues in there but the face came out better than I thought by trying out a beige color ;warm; no I know that because my face colors changed I can now do the fur warm and see how it compares in contrast to the face.,balaned, next section I'll see the face and fur measure up to the nails...all about balance and speaking color theory always for the most part use combinations of cool and warm tones so like jar head says shade cool complementary and highlight warm analogous..complimentary colrs are opposites on your color wheel (example red/green) @analogous colors are colors next to one another on the wheel (red,orange,yellows).hope this helps clarify why most of us do it this way..but again the base color ,wash, highlight this is not wrong they are preference.but if I may advise you briefly start to hone in your skills of 2 brush blending and color theory..probably the 2 most important skills one needs to learn that will help all sorts of skills to spawn from .example you can't do non metallic metals without first knowing how to smooth transition gradiants from 2 brush blending.