A: Hi there, Bernd, thanks for your question. I guess this was already answered here somewhere, but happy to give this an update.
The reason is simply that this is a tool that is meant to prepare and store the assets / social media posts that you usually need to / can use. This can also mean videos to be sent to YouTube as shorts, to TikTok, Pinterest (new) and most often (not surprisingly), we see it be used for posting reels and stories to Instagram. For those purposes it is anyway recommended to use not too big data (check out their info) and/or not too long videos. The 60 MB per file usually are more than enough for those purposes (for example a 20 sec. reel will download from Canva at max. 8MB).
For long form content (maybe sth. more lengthy to be published to YouTube) the recommended way to publish is to go the direct route - it will also there take some time anyway (why double that up?), special settings and can easily be set to be published at a certain time/day.

Hope this helps - Kristin [Founder + Product Lead Ägile Ässets]