Why is it not possible to export initiative contributions from the Explorer section?

When exporting in TXT or CSV format, it is not possible to include the contributions of an initiative. The number of contributions and their placement (rebound on the context / rebound on the description / rebound on the results / rebound on an existing contribution / etc.) would require a large number of columns to be displayed properly, or alternatively be grouped in a single column — which would mix everything together and make the data unreadable.

However, you can export initiatives along with their contributions in PDF format
(Exported Data > Content > Contributions).