The caveats section clearly notes that users shouldn't expect that a template allows its styles to propagate outside it. But a simple syntax that may be used instead is basically using the tag directly in an article, e.g.:
<templatestyles css = "Template:mypage/styles.css" > My article text goes here
Considering that most pages can essentially be used as a templates (except those with special content models), the distinction doesn't seem clear cut.
While some editors and wikis would probably be against such "ugly" markup there may be legitimate uses in non-mainspace pages or even in a main page for example.