It's to do with the properties of the font and nothing to do with appearance/effects.....
It's basically so the font becomes an image rather than being type. See, if the printer opens your file and you have some fancy "metal" font and they have not got that font installed (or at least have access to it), their computers will more than likely substitute it with something like Arial (thus making your artwork look lame and not as it was intended)
Open your file in a program like Adobe Illustrator, select the type layer(s), then choose 'Convert to Outlines' from the edit menu.