Snails and hermits will eat the left overs that the fish have forgotten, and its gotten stuck in behind the rocks. Over time this will build up and your tank will turn to crap.
Also, snails, Turbos, will keep your rock clean, I don't know of anyone that removes their rocks on a weekly basis to clean the film off of it, it gets the same film algae that the glass gets. And yes, its much faster for us to clean the glass, but the rocks?? Really?
A variety of snails, not a ton of them, a handful, 5-10, are easily enough for a 60g tank. 5 Turbos, 5 Bumble Bee Snails, will keep your rocks clean and will not starve out.
Lastly, unless you plan on keeping strictly SPS
, then no ones tank is that clean, as LPS
and Softies tend to like some phosphates and some nitrates.