People who prefer encrypted local backups. People who have local media libraries. People who prefer to use actual computers to edit photos and videos. There are plenty of reasons non-YouTube people still transfer files.
Not everybody has the same workflow, requirements, knowledge, or budget. Some people may not be a "professional" and this phone is Good Enough(tm), but they still want to edit their photos and videos. Some people may not be able to afford to pay rent on Apple servers to store terabytes of data. Some people may worry about the privacy implications of trusting servers outside of their control with their static data. Everybody is different with different priorities. It's annoying to dismiss people because they don't do things the way you think they should be done. (Not specifically directed at you but all of the people in this thread who are dismissive of those who might want to do the seemingly inconceivable and plug a phone into a computer.)