Re: "and run all the important apps"
> Yes but in your example, you need one person with a PC used for such things,
No. In that example, ANY person in the office needs to be able to do those things. Not only that, they may have to do even more interesting things that the OP didn't even get into. He only went into ONE small subset of the given use case. He only touched on the tip of the iceberg.
Flexible powerful systems allow users to do interesting and surprising things.
THAT is the whole point of the PC. You are not stuck dealing with centralized IT management to give you permission to do something. You just fend for yourself individually or collectively.
Mobile devices have to lose the whole mobile device cripple management mindset before they displace genuinely general purpose devices.