It has just come to my attention that some consider ‘the reason why’ ungrammatical or otherwise unfortunate. David Crystal mentions it in his introduction to Fowler's Dictionary of Modern English Usage, and this Oxford dictionary
Many people object to the construction the reason why …, on the grounds that the subordinate clause should express a statement, using a that-clause, not imply a question with a why-clause: the reason (that) I decided not to phone rather than the reason why I decided not to phone. The reason why has been called a redundancy to be avoided, but it is a mild one, and idiomatic.
As far as I can see, these ‘grounds’ are a misunderstanding. ‘Why’ does not ‘imply a question’ any more than ‘where’ in ‘the place where he was born’. It seems perfectly reasonable to me to say
the reason for which
which is the same as
the reason wherefore
which is the same, I would think, as
the reason why
So what is the problem with ‘the reason why’? I can see neither illogic nor redundancy in the construction. It is, of course, possible and often preferable simply to say ‘the reason he ..’ and ‘the place he ..’, but surely not always, and the objection seems to be stronger than that. Besides, I would rather say these are cases of omitting the relative adverb than call the full formulations redundant. Is the objection simply -- as it appears to be -- based on a misunderstanding?