Full Idea
A common view is that although a fairy tale may provide very useful predictions, it cannot provide explanations for why things happen as they do. In order to do that a theory must also be true (or, at least, an approximation to the truth).
Gist of Idea
A fairy tale may give predictions, but only a true theory can give explanations
Source
David Bostock (Philosophy of Mathematics [2009], 9.B.5)
Book Reference
Bostock,David: 'Philosophy of Mathematics: An Introduction' [Wiley-Blackwell 2009], p.290
A Reaction
Of course, fictionalism offers an explanation of mathematics as a whole, but not of the details (except as the implications of the initial fictional assumptions).