Localisation is simply getting your stuff accepted - locally. Consumers are 4 times more likely to purchase from a website in their own language, but true localisation goes well beyond that.
Everyone dislikes foreign instructions and incomprehensible packaging... or just that "wrong" look. Localisation is key where your product's interactive - websites, GUIs, or user instructions, or where your product needs to "fit-in" on the store shelf.
Translation only goes so far - localisation goes much further. Reflecting local style and culture, the result may vary widely from the source; Japanese packaging for example looks very different to European.
Localisation also helps avoid accidentally offending or amusing - accidentally amusing product names are a well-known minefield, but pitfalls can be much subtler. Localisation is there to help.
National style and humour vary widely - we've replaced jokes when our translators said "it's not funny here" (or once, "They'll get arrested!"...) UoMs, acronyms, style and more make or break your product abroad.