No. They are still in use. One typical usage of half-width kanas is the display of short texts on small devices of embedded systems, like status messages of control units, for example a one-line display, 30 characters wide, monospace, with 8x10 pixels per character.
Albrecht -----Ursprüngliche Nachricht----- From: Unicode [mailto:unicode-boun...@unicode.org] Im Auftrag von Werner LEMBERG Sent: Dienstag, 28. April 2015 10:09 To: verd...@wanadoo.fr Cc: m_k...@ga2.so-net.ne.jp; unicode@unicode.org Subject: Re: Why doesn't Ideographic (ID) in UAX#14 have half-width katakana? (...) AFAIK, the existence of half-width kanas in Unicode is purely for backwards and round-trip compatibility.