Take for example the HGUC kits of MSN-06S Sinanju and NZ-666 Kshatriya. These delicate tiny foil stickers would end up being more of a nuisance. They could fold up on themselves, be wrongly positioned, rip, come loose around bends, wrinkle around curves... I could go on. And, unfortunately, these problems also exist with the more necessary clear stickers, too...

But, with some patience and a lot of effort, you CAN get a beautiful result, even on these small kits!