This functionality is also useful for the localization of apps for various operating systems (e.g. Android and Apple iOS), as all placeholders (e.g. %s, %d, %1$s, and %2$d) can be converted into placeables. Upon completion, they are converted back into the respective placeholders. This prevents errors from creeping into the translation, saving the hassle of time-consuming correction cycles.
During the final quality management check, it is made sure that all placeables have been used and have been inserted in the correct order.
An aspect that should not be underestimated is that placeables do not need to be paid for, as they are not included in the word count. Thus, the use of placeables represents a win-win situation: You save money, and the translator saves time, as he does not need to research whether a product name needs to be adapted or translated. Moreover, the quality of your translation gets better, as the translator will make fewer errors, e.g. when processing product numbers.