Why the command noDisplay() clear all LCD screen?
I tried out your code. It's working absolutely fine.

Whenever lcd.noDisplay() executes then LCD not displaying hello, word!...
And whenever lcd.display() executes then LCD displaying hello, word!...

So, that's why "hello word" not continuously displaying.

And you can also find the display() and noDisplay() functions to turn on and off
the display comment on top of arduino sketch.