yeah i understand that point of view. But some cases sites do not allow wiki to be used with wide range of users, for example creating wiki that gives site users some help, tutorials etc. and authors are limited to small group like “team”. By this way it comes more handy to use. and if you create wiki that has wider userbase, you might restrict the “all inclusive” usage.
EDIT: and what comes to channel entry-based publishing, you are allowed to use frontend-forms to submit new entry - so why wiki itself does not work the same way like channels? You can limit channel entries to have only “safe html”.