ftr, you can now send media without compression on all platforms, including iOS: use “Attach / File”.
that way, you can send selected files and media “as is”.
some answers to follow-up questions in this thread:
we do not want to have a “global, always” options for that, as this easily goes wrong. one does not always know or care about receiver capabilities. it is also not the default user expectation that sending a few images end up in 100+ mb of data, let alone some minutes of video eating several 100 mb uncompressed. most user do not even know or think about that 
but we are considering from time to time if the current default compression is fine.
for multiple selection, and sending of compressed images: this is also available on all platforms.
for multiple selection and sending of files and uncompressed images: this is available on desktop, on mobile this is still missing, indeed
the latter is tracked at Ability to send multiple files and Feature Proposal: Multiple Attachments in one message - it is just not done yet. while we are obviously able to do things, we are short in resources and money. we have to weighten a lot. any donation will help https://delta.chat/donate