The potentiometer in most tutorials is wrongly shown connected with the ends to ground and Vcc and the wiper to pin 3 - the "Vo" or contrast control pin. This is a stupid blunder handed down from one bad design to another! It is also wrongly specified as a 10k value.
I'm not disputing the truth of that, but I have dug out an old Hitachi data sheet and it suggests a pot of 10k to 20k wired exactly like that. It also suggest the same but with a NPN transistor and 2 resistors to provide temperature compensation.
I don't know how old the data sheet is, but I'm going to guess maybe 1995 or thereabouts, it's an old, not very good photo copy.
If a pot between Vcc and 0V with the wiper on pin 3 is wrong then it is a mistake that seems to have its origins in the manufacturers data sheet.