When you think of a macaw beak, you have to think of it as a multi-purpose tool. It's primarily a third hand.
It can be used as a crow bar.
The sharp point on the end of it can puncture and slice things open.
It is used to test the strength of things before stepping on them.
It's used as a vice grip pliers to hold onto things, and rip them open.
And it's used to crack and crush things like nut shells... (or fingers that are someplace they are not supposed to be and/or are annoying us.)
The "beakier" macaws are just especially coordinated with their beaks, and tend to use the beaks as a first option, before they use their feet.
The beakier macaws tend to be a tad less patient, so when you "argue" with them, while they're putting their beaks on you, they tend to be a little more forceful about it. (Yeah, don't try pulling your arm away from a buffons or a scarlett after asking him to step up. Cuz they'll grab your arm first with their beak, and hold it steady while they step up... how hard they have to hold it to keep it steady, is completely up to you.)
And are more likely to use it to communicate:
Pinch! Hey, share some of that stuff you're eating with me.
Pinch! Let's go outside for a walk.
Pinch! I don't like that scarey thing. Don't you see how scarey that is? Pinch, get away from it. Can't you tell I'm trying to protect you?
Pinch! Pay some attention to me.
Pinch! Not now. I'm not interested.
HARD PINCH and/or BLOOD DRAW: What part of NOT NOW didn't you understand?! Can't you take a hint?! Must I draw blood to make my point?!