Yes, bokeh is a function of lens design, but it is very easily included in many types of photos. If we translate the Japanese word "boke", as Mike Johnston did in his series of articles in the early 1990's in Darkroom Techniques magazine, and we add an h to the end of it as an Anglicized pronunciation clue, we'd translate it as "the blur". As you've probably seen in much Japanese photography, both foreground and background bokeh are often used as pictorial elements, as building blocks, in photos. Bokeh is something that can be used to hint at or to show depth, and depth planes. Yes, it is a "function of the lens", but that's a rather meaningless statement when taken out of the context of using a lens to MAKE a photo...if you stop the lens down to f/22 and shoot a distant scene, and everything is within the depth of field zone, there is no bokeh...there is no "blur"...but if you open the lens to f/2.8 and shoot and have an out of focus foreground object, say a tree or an OOF rocky foreground, then you, the photographer have decided to use your lens's function in a pre-determined, artistic manner. Boke in the real, Japanese sense, is much, much more than just "a function of lens design".
Much of the tilt/shift and the "miniature effect" is based on the bokeh produced by a lens--the blur is what gives a very strong visual impression to images captured with a tilt-shift lens, or when a view camera operator uses camera movements to markedly increase or to markedly modify the way the blur is imposed upon the image.
While the out of focus rendering of a lens is part of the lens design, bokeh, or the blur, is also something the photographer can choose to use when he makes a photo. it seems that if you try to reduce bokeh to a lens-based issue, and nothing more, that yuo don't really fully understand what boke (Japanese, boke) really means. Utilizing boke is something I see constantly in Japan-based photo sites. Boke (again, Japanese word) is not just about how OOF light sources show up, it is not about how shallow the DOF is, it is something much more comprehensive than the reductionist dismissal you've given above, as if the LENS is the sole determinant of bokeh. Boke is much,much,much more than simply "a function of lens design"; it is a philosophy of image construction, a building block of making an image. Reducing the Japanese concept of boke to a lens-based technical issue is to miss the underlying concepts. Boke is an eastern philosophy about how one can perform lenswork. It's odd that you build up notan, and then dismiss bokeh so flippantly.