CJK characters is the one big weak point of UTF-8. It forces them to be 3 bytes large instead of the local codepage which is 2 bytes per character, or UTF-16 which is also 2 bytes per character.
IMHO a 30 percent size increase for sharing text data is really not a problem when most data sharing (by volume) happens via audio, video and image data which is infinitely larger. We obviously have both the bandwidth and storage volume to spare for those 30% increased size for text data which among all the other data would account for a tiny fraction of a percent.