I can see an argument that it can take a load off the parents by weaning babies sooner. But how is it possibly better for the babies to wean at such a young age?
It is better for the youngsters for several reasons. Nature has programmed them to progress at a particular rate of develpment. If that development is delayed, if the window of opportunity is slow in opening, it retards their development. In other words, if they rely on their parents feeding them for too long, they find it much more difficult to wean off the support and start to stand on their own too feet. To put it in modern jargon, they develop a culture of entitlement.
Another great reason of why it is benefital to the youngsters is that the amount they get feed is not based on what they want/need, but what the adults are willing to pump into them. The longer the youngsters are in the nest, the less keen the parents become in pumping them. This is particularly true in later rounds. Not all old birds have the same keenness to feed. If the adults start to back off, the young bird suffers and has no away to make up the difference of what it needs. If it has free choice to the feeder and can eat as much as it wants, it will not be deprived, so keeping the youngsters in the nest too long can actually be the cause of retarded development, not the other way around.
If you are relying on putting extra feed in the nest box so the youngsters will pick up the difference, why not just put them into the young bird loft and let them eat the entire meal themselves? To me, it is leaving them in the nest once they start picking that makes no sense. Why ask the old bird to do for them what they can do for themselves and why rely on the old bird to feed enough, when the hungry youngsters is pefectly capable of deciding that for itself?
It certainly doesn't happen naturally and for a reason.
What are you basing this conclusion on? In nature, city pigeons leave the nest in 20 days or less, and they have a much more difficult time finding food and water than domestic pigeons in a loft. If you are talking about letting nature take it course in the loft, the youngsters will stay in the nest until the adults quit feeding them and starvation drives them to the floor looking for food. Even at that, if old birds are willing to keep pumping them on the floor, they will accept the charity for as long as it is offered, 30, 35 days old or more. Most creatures are willing to accept a free handout if offered. That does not make it healthy or beneficial.
My opinion of a 28-day age-at-weaning is based on personally witnessing some young birds stressing out because they don't know how to pick up grains. They don't eat. They lose weight and mental faculties. They try to get other babies to feed them and they huddle in a corner confused. How can that be good for development?
I am not surprised that you have witnessed this. That is exactly what happens when you wait too long to wean. They have missed the important window and become dependent on getting fed instead of figuring it out for themselves.
If you wait until 28 days to wean, where have you seen this happen with 21 day old babies? Like I said, I weaned at 28 days for 20 years and then saw the light and have weaned at 21 days for the last 20 years. In my experience, early weaning is light years superior.
I simply don't see a reason TO do it, but many reasons not to. So what's the advantage? I open to learning (I mean that sincerely).
The only hard and fast rule in pigeon racing is that there are many road that lead to Rome. People can find success in the hobby employing many, many different methods. Unfortunately, the hobby is also fraught with a culture of sacred cows, myths and lore that is groundless and often harmful and can keep new fliers spinning their wheels by buying into these bogus beliefs.
I have found that it is best to look at the empirical evidence. What the old guy at the club that hopes for a smash because that is the only time he shows up on the sheet tells you, is often just a relic of the distance past, before the internet, before free long distance calling, before the honest and generous masters of the sport from all countries committed their methods to tapes, CVD's, seminars and the discussion sites.
We no longer need to trust our instincts on what sounds right or the word of any one person. Techniques are so easy to research and confirm these days, it amazes me how some of these old beliefs continue to hang on.
When it comes to weaning youngsters at 21 days, if you haven't tried it, it is difficult for me to understand how you can knock it. And I mean that with no disrespect. The beauty of this hobby is that every single participant is lord and master within their own lofts and we all need to do what we feel is right. In the meantime, it never hurts to verify.