>>6592133Because it IS a prototype. They're hand painted because the factory paint apps aren't set up, obviously. And seeing as how they're pretty unique until the mass market toy comes out, the prototypes are shipped around heavily. From conventions, to photoshoots, to marketing presentations, etc. All that moving around means that the hand painted apps tend to get chipped and often joints break. Take a look at this prototype Batman from 2017 Toyfair for example.
I thought this was common toy knowledge. How did you not know about this?