A Whether you want to keep those extra files is a matter of who you want designing your fonts: a human being capable of making aesthetic judgments or an application's algorithm.

Caption: Windows can give you bold and italics for any font (upper line),
but you'll be happier with the results from properly designed bold and italic fonts (lower line).

Font designers often create bold, italic and bold italic versions of their fonts, finding visually pleasing ways to darken and slant the letters. Windows, as well as your applications, use these if they're available. If they aren't available, the apps extrapolate bold and/or italic effects by altering the normal font. The results are never as nice as the special fonts created by a professional designer.

In other words, if you care about the look of your printed text, you'll keep the bold and italic fonts.