Blizzard copied GW, for both Warcraft and Starcraft.
Their original space marines were copies of 40k space marines. Their 2010 updated SC2 marines were copies of the new heroic proportions for GW marines.
On the "clean" point, from a hobby side it's because of GW's competitive advantage. GW pushes that aesthetic because they're really good at creating gloss and metallic paints, and pretty mid (some would even say bad) at creating realistic matte paints. So they want everything to look best if it is painted with GW paints, which means that aesthetic.
Blizzard copied GW, for both Warcraft and Starcraft.
Their original space marines were copies of 40k space marines. Their 2010 updated SC2 marines were copies of the new heroic proportions for GW marines.
On the "clean" point, from a hobby side it's because of GW's competitive advantage. GW pushes that aesthetic because they're really good at creating gloss and metallic paints, and pretty mid (some would even say bad) at creating realistic matte paints. So they want everything to look best if it is painted with GW paints, which means that aesthetic.