There are Tons of Functions not in QB Online; just ask the people using QB Enterprise. For my own clients, nearly none of them can use QB Online; it doesn't manage Job Cost from payroll and it doesn't manage Class Tracking to the same degree as Premier "Accountant."

If you have been involved with computers long enough, you would remember it has swung back and forth:

We used Mainframes, and the "computer department" was like Mount Olympus; only the Geek Gods resided there. The rest of us mere end users got Terminals = dumb interface tools. Then, we got Distributed Computing = the Power of an actual computer right on your desk! Then, we were told, "Let us keep it safe for you in The Cloud," and Lo! There was the return of the Geek Gods to take care of everything for you. Well, as long as you don't mind Not having it in your control, and as long as you Can Connect and Stay Connected to the internet, etc.