I just thought about it while reading this thread, but using the option can be a good way of checking how much latency is introduced by the VST(i) s currently active, even if bypassed.
This can be useful in determining which plugins, like reverb for vocalists, can be used while recording, without making it difficult to perform with foldback.
When you enable ASIO-Guard, the ASIO-Guard Latency shows the ms that the signal chain introduces. You may not leave it on, but at least you know the effect that the aggregated plugins are having.