Even on a standalone (not connected to a network) single user Linux workstation, different things happen in the background. Just turning the computer off may interrupt important operations and leave the computer in a problematic state (or at least some subsystems). Turning the computer off may cause problems, but in most cases it won't. It really depends on what is going on at the precise moment the power is removed. Here is a small list:
cronjob; turning the computer off may leave the databases unuseable.