Same here. Curiously(?), I always speak it as "point four seven", but write it "zero point four seven". The zero is implied in written form, and omitted in spoken form.
All about minimizing ambiguity. The spoken word should be concise, so that the listener is not burdened and fatigued by irrelevance; while the written word should be visually unambiguous, and can take some liberties with concision(?).
As most readers verbalize written text, one cannot take too many liberties on that aspect, or the reader will be as lost as the listener.
It often looks better too, though sometimes it doesn't. There's always a solution that is both appealing and sensible. Lazy drafters tend not to look for them (or think about appeal or readability at all, for that matter).
Tim