E-mail from a colleague I’m in contact with made me think of your post recently. (Context: discussing her school closure due to SNOWMAGEDDON up in Seattle):
Sounds like she is have a pretty sweet snowcation. So, yes, おかげで has another usage, which is closer to the ので and で that I wrote about in the past – it’s explaining causality, in particular beneficial causality. Because of/“thanks to” the snow and the school closure, she’s been able to read and study French and do yoga and damn you for living in a cold climate! I want a snow day! In the sentence above, おかげで is used at the beginning of a sentence, but you could easily use it as a conjunction and mash the clauses together: 休校になったおかげで、久しぶりに読書した。
This is the way that I first learned おかげで, which is partially why I was confused when I heard it as an idiomatic greeting. I knew that someone was being thanked, and I may even have had a sense that the someone had been dropped (pronoun drop yo) and was an implied “you.” But “you” hadn’t done anything for me! So why was I supposed to be saying お陰様で元気です? Because that’s what they say. When used as an idiomatic greeting phrase, you don’t have to consider the “beneficial causality” as much.
There is an equal and opposite conjunction せいで which is used to explain negative causality. For example, 雪が降ったせいで、自動車事故が増えた。
Personally, I loved watching all the videos the last few days of Seattle drivers running into each other in the snow because that’s exactly what would happen in New Orleans. I, however, mastered snow driving in Fukushima. The best policy is just not to drive (as long as you have sufficient supplies of chocolate and beer).