There are numerous plugins (e. g. Tasks) that each use a different and often either badly or not at all localised custom input component for selecting dates. The result is a horrible UX mess. While date inputs are not part of Obsidian Core they are such a common scenario that I consider it both feasible and desirable to add them to the core.
Having a canonical date input available in the API would both reduce code redundacies across plugins and vastly improve the UX for date inputs.