Provence said:
/sbg is simple background.
And your first paragraph is exactly what I'm saying:
1. Images who are too good tagged and get this tag.
And then there are images that don't have any or extremely few tags (laziness).
And if only one or two tag is missing:
I think that forum #12251 is the more appropriate place then tagme.
I think we both agree on that - that's why I dislike tagme: even with the wiki definition, people use it thoughtlessly more often than not. I've only really tried it when I was first uploading, and stopped when I realized that more specific request tags or asking for help in the comments got better results. That, and actually using the search to identify characters and tags using common physical descriptors and the like.
It's not exactly hard to hit level 2 tagging, as long as you get the bulk of what a search for that image would use as common definitions (monochrome for uncoloured sketches, prominent hair style or physical/costume characteristics, copyright). If your can get that far, got shouldn't need the tagme 95 out of 100 times. Asking for help us much better for all involved - for the Uploader who needs to learn the right term, and for everyone else looking for pictures like that.
Basically, you tag the characters, what they're doing, what they're wearing, and how they look, and you're basically good. Tagging background and number of characters/gender is good for more mechanical searches, and is relatively easy compared to tagging copyright of character names.
If you're using tagme after getting all of the above? I don't know why anyone who wasn't being lazy would.