A data "stream" consisting of a single frame can
require a network device to do a lot of processing.
Figuring routes, performing ARPs, checking
permissions etc., in general, setting up cache entries.
Devices will often take much more time to process a
single frame presented in isolation than it would if
the same frame were part of a steady stream. There
is a worry that some devices would even discard a single
frame as part of the cache setup procedure under the
assumption that the frame is only the first of many.