>>9819253Okay, I'll bite.
When filling, sanding or doing any modifications to a model that changes its color, it's impossible to see the shape by eye. Primer not only helps you see the shape, but it also helps you fill in the shapes by flooding it, since it's almost always sandable synthetic resin primer that people talk about, not that acrylic garbage. And because I know you've never tried, no, you cannot sand acrylic or enamel paint.
When doing any sort of weathering, especially rough effects that require you go in with any amount of force like dry-brush oil color modulation, you can often scape off paint if it was painted directly on plastic. This is especially prevalent in acrylic paint. See pic related for instance, I've had to cover it up and it took like 2 extra hours of work. Now, I realize that saying "no trust me bro there's a really a big difference I've painted both and I can tell" is not enough, but this is the best I can give you on this particular argument.
While these two are reason enough to use primer for me, an extra bonus is that the coverage of primer is fucking fantastic. I've done away with all white paint and just replaced them with primer, and I've done pre-shading with black and white primer ever since. And no, you cannot "just do it with other paints lmao". white paint cannot replace white primer, because the coverage of white paint is trash.
