From the Advanced Bash-Scripting Guide:
The special symbol << ... is similar to interactive-program < command-file
In fact, everything I can think to do with the
<< here-document symbol, I can already do simply with
< command-file or
<<< 'list of commands'. Namely, I can do
cat < <(echo fdsa echo asdf)
cat <<< 'fdsa asdf'
cat << a fdsa asdf a
One (obvious) exception is, in case you want your command list to terminate differently, depending on what terminating parameter you pass in. However, I cannot think of any situations where that might be useful.
Another exception is, that using a here-document allows you to place special characters, such as ', into your output without worrying about how to escape them. However, this too, seems like more a convenience than an essential feature.
Where else might here-documents be so essential, that Unix reserved a special operator for them?