Just because something has been done for decades doesn't mean there isn't a better way to do it and it doesn't mean the old way isn't the best way either. I am trying to make a decision for myself.
You sould like a pretty big meat head, I'd like to train out in Vegas sure, but your attentions are clearly to make yourself feel important.
I didn't disbelief you, I was unsure of the reason so I was hoping for some intelligent responses which obviously won't come from the likes of you. I'll look at your log gladly and maybe I'll learn something from it.
It isn't obvious though and that is why I am curious about it. I think the most obvious answer to me is that they do it out of tradition. I don't think it is a good idea to do something that you don't understand when the answers should be accessable from the boxers here despite what you think being rude is.
So when someone answers your question, and even invites you to train with them, the best you can do is insult them? Wonderful.
I sound like a meathead? What precisely does a meathead sound like praytell?
And out of the "Boxers" here, there's only a couple that are actually training a Pro system, which is Worlds different than an amateur or a "just getting in-shape" system. So the answer you seek could be variable upon the person. If you want an answer from a Professional standpoint (which that's what it seems because not even all "Boxers" do a lot of sit-ups), you're going to get a little flack for that because the answers are right in front of your face if you even look at Boxing at all. But let's address some of your questioning issues, and your ideas of telling people how to train despite never a day in your life training a regimen designed to succeed in this specific sport (which I did a whole thread on why not to take the tone of "I don't get it, there's better ways" about Sports rich with SUCCESSFUL traditions"). Okay? Let's begin at the beginning:
I can see the importance of getting strong abs through heavy deadlifts and low rep ab exercises.
First of all the problem with this is that Boxers below the heavyweight division do not traditionally lift weights. Now we've had every debate as to why, and I personally have never seen a reason nor viable example to stray away from this tradition. I myself fight at 147, but I walk around heavier. With as much training as I do (2 sessions per day, up to 6 days per week), fitting in weights would just be too much. The floor exercises give me as much strength as I need without the risk of either injury or just plain overworking the muscles. Cardio is much more important, as is muscle endurance, for which high-rep bodyweight exercises are much more viable. One could argue high-rep weights are just as viable, but again, there's just not more reason to do that versus floor exercises. Now out of the routines of many many former World Champion Boxers I've seen, I've only seen two lower weight class fighters take exception to this. Kostya Tszyu and Ricky Hatton. Hatton has a very odd style dependant upon physical strength, and his body-type responds well to weight training, and also he detracts from other areas of his training to add in the weights. I doubt very few other people have his natural gifts, so there's not a whole lot of reason to copy his routine which features weights. Kostya Tszyu is a physical exception simply because he's gifted as an athlete to where he has astonishing muscle endurance naturally. So his body can withstand both lifting and a full Boxing regimen. This is very rare. However the very simple floor exercises + running + technique training has led many people who are not exceptionally gifted to World Titles. So what's better? A basic formula that works? Or people who have never Boxed or won Titles telling people otherwise?
I can kind of see doing bodybuilding reps to enlarge your abs for added cusion.
No one in Boxing wants large abs. Remember, Professional Boxing is also a gambling Sport. Hell gambling is most of the Sport's vitality honestly. So, if they see someone with large abs the betting odds are going to go one way. One could argue this is good because you could have someone you know bet the farm against you, but it won't always work out that way. Reason being agility is very important in the ring. Having large abs could get in the way of this, it could throw off the dimensions of torquing and twisting the core to be able to punch properly, and bobbing and weaving to avoid getting hit. Also in Boxing, bigger bodyparts = bigger target. Even if someone's abs had added cushioning, if they were distended, that's where I'd be punching. If I focus on that, chances of landing a liver or kidney shot are increased. Now, looking at someone with a toned flat 6-pack it has the aesthetic ideal of being like a sheet of metal. You're not so sure if you punch them there it'll hurt or not.
Now, if you WANT to not do sit-ups because you're afraid of them you can make any excuse you want. Like using the internet as a means of making a decision based in opinions of people who don't do what it is you're asking in the first-place (which should be taken into consideration). I'm not saying that's your perspective, but I'll know by your response, which will be if you take every viable reason in the Professional game I gave you and attempt to dismantle it when odds are you have never trained this way a day in your life.
This is the reason I called it rude. It's simple etiquette. You don't walk into a Muay Thai gym and go "Why do Muay Thai guys do a lot of kicking drills, I mean pshhh, there's better ways, I don't understand." The best way to make a decision, find out how they train and do what they do. If it works, stick to it.
Just keep in-mind that what you're questioning here are not simple gym practises that people with no credibility are feeding you. You're questioning things that have been done by and continue to be done by people who win titles, and make money doing this. So don'tbe shocked if they're a little touchy about it. The simplest answer is they do it because it works.