Originally Posted by
mpetry912
yes, you are right, with a long enough cage and careful selection of chain length, you MAY be able to get the chain to wrap the large / large or small / small combination on a triple, but why ? Both are at the extremes of chain tension and slack, and also friction and wear associated with cross-chaining are at a maximum, but more importantly, the gear ratios of both combinations can be approximated by less extreme selections of ring and cog.
Large/large is a safety issue. It's not an issue of being able to use it, it's an issue of not having the drivetrain implode if you accidentally do. Small/small, well I run cassettes with small gaps and 11t at the top end. It's useful for stiff headwinds and trying to stay in the goldilocks gear.