Isn't that just sleep mode like the PSP/Switch? I reckon it saves a bit of battery and turns it off and goes to sleep mode like many systems, unless I'm missing something here.
Yup, it's not just for when the battery dies. Pushing the power button on either doesn't completely turn the systems off, just goes into sleep mode and doesn't take up battery (extremely slowly), and when you power it on again you're right where you left off.
The Vita is quite handy. I almost never need to worry about the battery. Last time I charged my Vita was sometime last month, the battery is still at around half.