There are some advantages that I see:
1. I have read that when tying fluoro to mono, the different physical properties cause the fluoro to "cut' the mono, making the knot less secure. This may be obviated by using a tippet ring between the mono and the fluoro.
2. Fluoro does not degrade like mono does after a couple of years. This means that it can be stored and used for a decade or more, unlike mono that becomes brittle after 2 or 3 years.
3. Fluoro is more abrasion resistant than mono. Of course, using a fluoro tippet may provide an abrasion benefit without using a full fluoro tippet.