Firstly, what is the exact purpose of the phrase "or (at your option) any later version" that usually accompanies GPL-licensed software? I get that it's supposed to be to allow future freedoms to be granted, but why is this particularly an issue with the GPL such that everyone includes this phrase?
Secondly, does this not also work in reverse? So if for example version 4 removes the restriction for modified source code to be supplied alongside the binaries (hypothetical example) then that would mean that people would no longer be obliged to provide the source code, even for older software (because they could choose to redistribute under version 4 instead of version 3). So this phrase not only allows the removal of "bad" restrictions from later users, but also retroactively applies the removal "good"/"important" restrictions so that later users are no longer bound by the same terms that the original developer intended. It surprises me that no one seems to be concerned about effectively licensing their software under a license that doesn't exist yet and that they have no control over.
Finally, what would be the implications if I were to remove/omit this phrase when distributing my software, and how exactly can I ensure that this part is completely removed/not applied to my software? Is omitting this part generally frowned upon and if so why?