Kit manufacturers these days seem to have the people who don't like to/or can't for one reason or another paint the models.
Many kits these days are molded in color, or at least pretty close to color. I have had a few kits from Academy now that do this, and of course Bandai kits as well as Meng kits and even the newer AMT/Round 2 kits like the Space 1999 stuff or Razor Crest
When these kits are molded in color, in theory, you could skip painting the base coat. However, they still retain that "plastic" look.
One thing you can do to help alleviate that is to dull coat (or matte varnish) the model and do some basic weathering/wash.
It goes a long way to improving the model
For example, here I just could not seem to find the right color I wanted for these Space Battleship Yamato models at the time, so I simply first sprayed them with Testors Dull Coat to get rid of that plastic "sheen". YOu could instead just spray with a matte varnish, but I like the Dull Coat since it gets it really flat looking
Then I used some oil paint drybrushing and sludge washes plus some Tamiya weathering powders to get some tonal variation and some other hand painting to maybe get some detail parts like the antenna to look metallic. In the end, while not quite as good maybe as if they had been painted due to the natural variation and allowing undercoat to show through etc.., it still turned out nice enough in my opinion
So again, no base coat, simply straight to weathering over dull coated plastic