I think that you may have a point in some cases. Sending updates out when you're just repeating things is not really that much of a help. However new things do come up that are not possible to mention in AMCAS and secondaries, especially if you submit applications early. In my case, for example, I received an award, found out about a new conference that I will be presenting at, and began work on a paper that my college lab group will be submitting for publication (and for which I will be a lead author, which I was not aware of previously). In addition, I started a new research job in June, which was around the same time I submitted my AMCAS (and right after graduating), making it impossible to talk about this in AMCAS. I therefore felt that an update was necessary. I do think that it's important to wait until there are a few things to talk about, or large developments with one thing, before submitting an update.