Why can't you restart PCs immediatly after cutting off power while the PC's running?

Question

I noticed that after cutting off power supply while the PC is running, some PCs can't be restarted for a minute or so. Why's that?

This is different when pressing the front power button for several seconds. Then, restarting works immediately.

Answer 1

Certain PSU's have a safety switch built in. This stops the PSU from being damaged when there is a sudden power failure, or a continues power dip that causes the power supply to switch on and off rapidly, which generally destroys the PSU.

I lost 2 older one's like this. Thankfully the newer one's will delay restarting long enough for the PSU to not "pop". This switch is only activated in the case of a sudden power failure. There is an actual patent for this you can read about here.