Redmine

I'm a real rookie about Redmine, and I'm trying to understand when to use each functionality available for project management in general (not only for code development).

I want to understand the benefits of using SVN as a repository associated with Redmine - my (crazy?) thesis is that one could use the Wiki repository, for example. Let me explain:

I've seen that through the Wiki one can consult diffs for all the wiki page history. So theoretically you could for example create one page for each target version, and for every file in Redmine's code you could create a correspondent page, where the content of the page is the file content itself. And you would change the code directly in the Wiki. All permissions controls would be done through the Wiki, to avoid vandalism.

Anyway, what I would like to understand is what are the advantages (which of course I understand that there MUST be!) of adding one more layer of control by integrating with SVN for example. And if this (crazy?) proposition of mine would make sense in any context.

Sorry if this is just absurd, I'm just proposing this discussion to better understand this whole thing... Thanx!