PC's are still the primary computing tool used by office staff and I don't see that changing anytime soon. There's too much specialized software written for Windows, and the famed MS-Office compatibility issue still lurks. You have to mirror MS's bugs to be fully compatible.
PCs are basically back to what workstations were, though with much broader price-points.
Even ignoring Windows and MS-Office, workstations are better for work than phones or tablets. Even though everyone at work has email on the phone, the vast majority of people send emails from their PC, though they may check their email on their phone. Web interfaces to ERP or other systems is much easier done on a PC, if one is available. Let alone specialized applications like CAD, IDEs, etc.
Phones and tablets fill in a lot of what "Home Computers" were. Significantly lower administrative overhead than a PC or workstation, generally a lot easier to switch on and open an App (technically it's waking from sleep). Plus they are always with you, so you always have all your data and Apps. Though they are really terrible at actually doing real work.