<i>I don&#x27;t understand why nobody else is able to do it...</i><p>Because they don&#x27;t care, need to, or want to? Google and Microsoft are competing with Dropbox on economics of scale and perhaps as a loss-leader. A lot of people are willing to forgo peer to peer LAN sync or block-level syncing when the cost is much lower. Additionally, both Google Drive and OneDrive have an integrated office suite, which adds value for a lot of people.<p>Moreover, if you can get away with a weak client, it&#x27;s an advantage. Someone who has all their data synced to disk can easily switch. Someone who has their data primarily in someone&#x27;s cloud cannot as easily.