Practical uses of readv?

For this first time in sixteen years, I came into a situation where
readv (recvmsg) was actually useful: In order to dump the
'non-ESP marker' in front of an ISAKMP message when NAT-T is being
used for a particular 'IPsec session'. So far, I've assumed that
'scatter read' mainly exists for symmetry reasons. Anyone ever used
that for anything? And if so, for what?
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