They could decouple the video download from the app download. Then they could even update the video independently if needed. Not everyone that downloads the app needs the videos, and even the ones that do I’m sure would be happier to reclaim the disk space after viewing them.
It’s lazy.
I often use the DJI MIMO app while out of WiFi, and would rather not download a large video separately. For the record, I do not like the DJI MIMO app (because it is the only app for their 'Pocket' products, and MIMO doesn't support tablets well), but I think this decision is a reasonable one.
You'd rather just keep every tutorial video in your phone's limited storage, forever?
The more likely outcome: because the app is huge, you'll uninstall it to save space. Then when there's no signal, you have no app at all.
I did consider this, but I'm curious: what are you doing that you need to watch a video out of internet range, that you couldn't have done while testing things out while in range? Isn't it risky trying something for the first time in the field without having already practiced it? I do understand that not all things can be anticipated.
800 MB High resolution video explaining how to connect a microphone is still bonkers. There's no justifying this garbage.
MIMO also manages many different DJI cameras (badly).
Gmail has no such excuse.