CJK(V) is just a collective name for countries that use or historically have used Han characters, and the main reason tends to be a lack of alternatives. Korean had an alternative for almost 6 centuries, and while it took a very long time Han characters are now virtually extinct in the Korean language (despite some people arguing otherwise...). And other languages don't need 40K characters to learn anyway, it's around 5--10K characters IIRC.