There's nothing wrong with hitting full shots. But if I'm 60 out, and know my 62 punch with backspin will go 60 yards, its a hell of a lot easier than choking down a ton on a full 75 yarder. Same thing for anything 30-41 yards, its much easier (imo) to choke down 0-20% on a 41 punch than choking down a ton on a full 50 yard. I personally am forced to use it more than most due to a 90-115 gap in full shots, so I go to 98 punch when possible.
Some holes simply receive a lower trajectory punch shot better than an abrupt stopping full shot. Also as mentioned earlier, punching 3w is very often your best bet from rough. All in all, many many many opportunities to use the punch shot (many not listed, where you have to think outside the box and experiment).