Data caps make that hard. While everyone likes to claim unlimited data, I'm not aware of any providers that don't have a heavy data user clause where they'll deprioritize your data if you're a top ~5% data user (usually somewhere over ~1TB/month).
You also will need _some_ sort of encoding locally before uploading, even if it's minimal, which could lead to issues when encoded again (although there are codecs available to minimize this).
Just over half the world’s smartphone users do (meaning almost half don’t), and certain countries/areas have way more coverage than others. And a massive number of people have limited data per month, which means it’s also a cost concern.
Leaner delivery is not just ethical, but it also makes better business sense.
You also will need _some_ sort of encoding locally before uploading, even if it's minimal, which could lead to issues when encoded again (although there are codecs available to minimize this).