The rational would be that people often want to construct matrices (i.e.
even where the elements are themselves arrays and they do not want
concatenation) and that there is no syntax for this. All the tricks with
reshape or transposing are not very feature proof, as e.g. transposing
might change at some point to return a dedicated Transpose wrapper type
that doesn't actually tranpose anything and reshape is currently also being
reconsidered for returning an explicit view in the form of a wrapper
ReshapedArray.
