Well... RFC 953 specifically mentions using PORT to send a file to a line printer so that seems intentional. [1]
For streaming mode STORe/RETRieve the connection closes at the EOF so you could send the request but the response would be lost.
[1]
It is possible for the user to specify an alternate data port by
use of the PORT command. The user may want a file dumped on a TAC
line printer or retrieved from a third party host.
It probably seemed like a good idea at the time, and there was no way to know the problems without trying it.
It also allows you to send a command to cancel an ongoing transfer.