"We've never localized this product/module/component/blidget, so it doesn't need internationalization."It's a good thing that nothing ever changes in products, nor in markets. Oh, they do? Yes, even though your product has never been localized before, and this may be a real shock, it might be localized in the future. Whoa! And, another shock, localization is a business decision, not a technical decision. In other words, if a customer says, "We'll buy 2 million licenses for your product if you localize it into Cloqrat," you don't want to have to say, "Gee, sorry, it'll take a massive reworking of the code, say, 12 months to get that to you" since your customer will respond "That's OK, we'll just buy Microbrain's version" and then your problem will be solved because you won't ever see that customer again.
But there's more to it than that. Internationalization is a lot more than making the product localizable. It's primarily about data processing (see Myth #1). That is, even folks in the USA have to process data that is not US data. Was that another shock? I'm sorry; try some rooibos tea.