It’s a fair question.
You want to ensure everything is ready to go – you launched your product in the original market and in the primary language. Your content is perfect, your images are selected, your audience is responding very favorably. Now you are ready to move on, to expand to other markets/locales. You define language(s) that will optimally deliver your message to those highly desired new users/customers, etc. Translators are hired; you even remembered to secure a QA team. Great! You will have your multilingual product in no time! Simple. No so fast.
As Translation vs Localization points out, translation is not enough. Marketing copy can be especially demanding on translators; transcreation might be required. However, even that is not the only challenge. Localization is much broader than translation. It includes a whole complex of technical and programming elements outside of translation alone. It involves adapting information to a particular market and national mentality, translation of site programming modules, adapting graphical interface and site code, to name a few.
Because of that, localization should begin before the product is finished, not after. It should be part of the product creation process. Think big from the start – it will pay off.