On this site in particular, the fraction of questions that need schematics is not what it is on electronics.SE. The thing about schematics though is that when you need them, you really need them. Electronics is certainly part of ham radio. As proof, I reference the question pool. Each level of test (technician, general, extra) contains at least some schematics, with 20 in total. If it's important enough to be in the FCC exam, which tests for a very basic understanding necessary to be licensed, then certainly it's important enough to have here, where hopefully we explore above and beyond the level of understanding necessary for licensing.
Looking for example questions, I'm not finding many. Most are of the "I can haz codez?" variety, such as Simple DIY AM receiver for 25/28 MHz. The most legit need for a schematic I've found is Using a Morse code key with a computer?, but that's well served by including some images.
Still, I would want the ability to include schematics, because I think people should be asking questions that would require them, even if they aren't. Perhaps this is a case where a desired (at least by me) behavior (more technical questions) would be encouraged if the tools were more available. Or, this may be a case of my wanting the site to be something it's not.