Surely you can just simply follow them in to ensure the third shot lands. Watch a boxer, kick boxer, mma guy etc even though it is normal to ensure your feet are planted when you throw a shot to generate the most amount of power, fighters will shuffle, slide, step forward on each shot they take.
In training this then simulates that if the 1st or 2nd or both shots land you have moved forward in order to compensate for the opponents backward movement in order to make sure that your 3rd shot lands.
I have never personally been taught to throw a multiple punch combination and remain static, should always move whether it is a shuffle, slip or step to ensure that your 'punches in bunches' hit the target and you are not simply flailing in the air and wasting energy.
If you follow them, their right is often not an open angle. Itd be easier to do another jab, then go from there. Plus. youre opening yourself up to their jab, if theyre retreating. From which they can counterattack. To put it another way, how often do you see a 1-2-3 land, that isnt a 1-2-1-2-3 type deal whilst the other persons up against, say, ropes?
I always thought the hook was to get them to drop their guard and maybe work on fatigueing them but admittedly my boxing experience is limited. So, are you going to enlighten us. You have had some interesting perspectives in the past.
Gnarlie pretty much nailed it. Opponent slips the right hand, you follow them with the hook. It can also work, in a different way, if your opponent ducks.
Its a defensive punch - If youre chasing them, its not going to be much good. Plus, lead hooks are a tad harder to throw whilst moving. If their right was open, youre better off leading with the left hook. Or a right cross followed by left hook. Thats what i was taught, anyway. And ive yet to see it work any differently.
If youre trying to fatigue them, then pin them down. You do that by having good defense and maintaining pressure. If you want them to drop their guard, you need to do more than just go to the body. If you go low, now they can go high. Youre giving them a target. Body shots either need to be in tight, or set up. The only way theyll drop their guard is if theyre set on stopping everything coming at them.
...All from the perspective of a person who did boxing for quite a while. My word is not law, nor do i claim it to be. I just know that 1-2-3 aint that good in offense, and has limited/specific defensive uses. And all told from the perspective of boxing.