" "ID" seems to apply almost solely to a literal interpretation of Genesis: seven days, Garden of Eden, etc. No symbolism allowed."

Why? Well, whether most people even understand the term, "anthropomorphism" is involved. God is endowed with 'lonliness' and 'deciding' and such by many.
The other aspect that *I* am convinced of is that "ID" is just easier as an answer. No complex studies and pondering all the science of physics & cosmology.... just assert "God made it, and He knows how & why!", and you're done!
(This also allows such logic as I recently read from one of the injured survivors of the terrible air show accident. He was near the site, and ran, and woke up in an ambulance. "I guess God was just with me." IF you do the full anthropomorphism, it awkwardly 'follows' that God 'chose' to save some, and only He knows why.)

Humans are just simply capable of denying or accepting odd bits of reasoning.... it is called rationalizing, and we all do it at times....some just use it for their basic approach to living.