From wikipedia...

    UTF-8 always has the same byte order,[5] so its only use in UTF-8 is to signal at the start that the text stream is encoded in UTF-8...
    Not using a BOM allows text to be backwards-compatible with software designed for extended ASCII. For instance many programming languages permit non-ASCII bytes in string literals but not at the start of the file. ...
   A BOM is unnecessary for detecting UTF-8 encoding. UTF-8 is a sparse encoding: a large fraction of possible byte combinations do not result in valid UTF-8 text.

That last one is a weaker point but it is true that with CSV a BOM is more likely to do harm, than good.