It seems like I see these words together everywhere these days. I don’t know if it’s always been that way or if I just started noticing it within the last year or two. I can’t explain why, but it just feels wrong to me in a lot of cases. Usually the sentence flows better if I replace it in my mind with simply “to,” or omit it entirely.
Probably the most common way I see it used is, *I’m curious as to why . . . *
Wouldn’t that sentence be just as correct written *I’m curious why . . . * ?
I don’t know. I have this nagging feeling that you need a preposition between “curious” and “why,” because “curious” is an adjective, but I don’t have a good grammatical argument for it.
However, I agree on your second point (although I hear it with only one “is”). (And the “myself” one, too.)
I agree that you should have a preposition (or a new phrase “I am curious; why are …?”) But I think “about” is a better preposition than “as to”.
However, I think it’s really best, if you asking a direct question, to phrase it as, “I am wondering why …” “Wondering why” to my mind gives a better statement that you are thinking about a particular issue and want an answer rather than just being curious.
Having said that “I am curious why …” sounds much better to me than I am curious as to why …"