Earlier quoted context omitted.
Dropbox is a company that hosts your files. If it was a feature of the operating system, who would host the files?
There are no good reasons I couldn't host my own files, with my own bandwidth, on my perfectly cromulant server/mobile device. The only issue is, it hasn't been considered of any importance to maintain user agency; better we steal the users agency over their data/computers, put it out 'in the cloud', and get them addicted/dependent on third parties, than to make the operating system deliver similar levels of service,…
Also, the battery can't handle your laptop open 24/7 just to serve a couple of files you _might_ need someday in your phone or other computer.