I assume that Microsoft have looked at the usage numbers for Outlook 365 in each of these languages and found that the number of users was tiny on iOS, less than the cost of translation and support.
I also assume that they continue to support those languages for Outlook 365 on Windows.
By comparison, many of my favourite freeware/shareware programs invite crowd-sourcers to contribute translations.
LibreOffice have provided the tools to localise the product into unsupported language.
I wonder if the new Microsoft could move toward this model of internationalisation/localisation (i18n/l10n).