Files with spaces and other escaped characters don't do correct escaping when dragged from the file manager into the Terminal. This may be a terminal bug, as unescaped characters might be desirable in other places.
What do you mean by "not escaped properly" - you want filenames dragged to the terminal to be escaped for the shell? What if people are running mc or tcsh instead of bash for example?
Good call. I hadn't really considered that, though the examples you cite would work with bash-style escaping in most cases.