Actually, it's not an acronym, it's a mnemonic ;-)
An acronym has to make a real word sound, such as P. A. C. E.
Or N.E.W.S. for North South East and West.
DIY doesn't make a word sound - we still have to pronounce each letter separately. So, it's just shorthand really...
Unlike "www. "which takes longer to say and as three times as many syllables as "world wide web", which has always baffled me somewhat as to why we use it when speaking...