Why 18K gold instead of 14K?

I prefer working with 18K yellow gold as it has a richer gold color than 14K and is what I consider a good medium material as it is 75% gold compared to 14k being only about 58%. 14K is stiff and difficult to work by hand thus it is usually a caster's material. My work is hand made and not cast thus I need a more malleable metal. The Thai goldsmiths complain that 18K is stiff to work with and they prefer 22K thus 18K seems to be the middle ground and it is accepted world wide while neither 14K or 22K is accepted world wide.