Italian and Japanese armed merchant cruisers

Why is less heard about Italian and Japanese armed merchant cruisers?

They achieved less than hoped: Italian ships were often sunk by British submarines, while Japanese ships sometimes met full cruisers.

The Italian vessels could perform well but suffered badly against Royal Navy U-class submarines. Japanese armed merchant cruisers had the further misfortune of meeting opponents built as true cruisers. Those outcomes limited the extended independent careers that make commerce-raider histories prominent.