"Turn off" is not the same as "shutdown".
Umm... it isn't? What is the difference? Except for OLDER PCs, and I do mean really, really old PCs, there is no difference. Unless you speaking of maybe some Sleep mode?
Look, let's summarize:
1. PRESS Power button - Issues Shutdown command that starts the PC Shutdown process that results in an *eventual* power off. The same 'blocks' will still apply (e.g the screen that pops up saying , so and so has not saved its work, or flushing of disk caches).
2. HOLD DOWN Power button - FORCES an IMMEDIATE shutdown - UNSAFE.
3. Press Reset button (if your desktop PC even still has one) - does an immediate unsafe restart (power off, then back on).
Otherwise, we're probably just talking about different things. You may mean 'immediate power off'. To protect users from themselves, this is not as easy at it used to be. You have to hold down the power button, flip a switch on the PSU (if there is one), use the reset button (if there is one), or unplug the darn thing.