Proper striking can be effective. I've put people down and broken bones with techniques ranging from hook punches to slaps. On the other hand, they're really idiosyncratic. If anyone tells you that a specific strike will always have a specific effect, the person is lying. Or misinformed. In my personal experience, I've taken a crowbar to the back of the head with no injury whatsoever, and a slap to the back of the head that left me dizzy and puking for three days. I've been lifted in the air from a solid kick straight to the crotch and didn't feel it for well over a minute... and I've been flicked in the crotch and gone down.
Strikes are dangerous. Even if you don't notice that you have broken bones until after the fight, they are still broken and can take a long time to heal. That solid shot to the head might not hamper you at all, until a few hours later when the tissue swells and you pass out. Maybe die. Hours after you 'won.'
Because of all this, strikes require special safety restrictions in training. Maybe you put big pillows on your fist. Maybe you pull the strikes and practice missing. But something is done to make sure that the strikes in training don't do what strikes do...
Which has two bad effects. One is obvious, in that all the training to miss (whether you call it pulling or just use contact to a safe area like simulating hitting the groin by hitting the thigh) will influence you to miss in real life. Trust me-- you'll have other things to think about than trying to remember what you simulated in practice and substituting the 'reality' variation.
The other bad effect is that it increases the value of grappling techniques in sparring.
That's not in and of itself a bad thing. The ability to move, control, lock and strangle a human body are some of the most effective and reliable base skills. But when you are practicing, whether sparring or scenarios, and the strikes have to be controlled and the submissions can go to submission, you wind up with scenarios that always end with a lock or strangle.
Unless you stay alert, it can seem like locks and strangles work and strikes don't. The thing is that real strangles work far better than pretend strikes.
I haven't found a good solution for this. If you insist that people respond as if the strike was real... what the hell does that mean anyway? Not everyone folds when punched in the torso. To be truthful, not everyone even notices when they are punched in the gut. Headshots are notoriously idiosyncratic.
One of the cardinal rules is that you never train people to fail. Giving up should not be part of the drill. If you teach people that if they get hit in the head (or stabbed or shot or blinded) they are out of the fight, they tend to simply quit when the condition is reached. That's unacceptable.
At the same time, if you have trained to tactical advantage, you discard techniques that don't work. Consciously or subconsciously, students will tend to reject the strikes and focus on the submissions in an environment where only submissions seem to work. That creates a weakness as well.
Yet another problem is that because of the safety artifacts, a grappler will usually have a huge edge in applying techniques in a free-for-all. Many strikers, except with gloves, have never practiced getting kinetic energy into another moving, dodging, resisting body. Getting peak force in a strike requires control of motion and distance and those are things learned best hands on. The strikers who use gloves are almost required to use hand conformations that put their metacarpals at risk, so they can play harder, but what they play at often injures the striker more than the strikee once it ceases to be play.
This one's a poser.