It does sound strange, doesn't it? But take the "Kuro was here" for example: It's not just opening a text field and then typing it in - that's sadly not really feasible in the program I'm using. Instead, what I have to do is to open up Inkscape, create the text in there, with all the shadowing and whatnot, export it as a .png file, then import that into Koikatsu, put it onto a plane object, find the right dimensions, and finally, play around with the shaders until it seamlessly blends in with everything else. Now, even that isn't a ton of work - especially, if you've done it a few times like I have. But it's still about 3-5 minutes of work for a simple bit of writing in the background. And like I said - those add up.
Exactly, that's my thinking! Yeah, some of them really don't add too much, but it's still nice to have them there - if only to add some flourish. And that's basically what they are. (Unless they turn out to be extremely loveable characters that I elevate to a more significant status within the story :P)