It is ridiculous, but if you think about it, it makes sense why it became this way. Yet another good idea that got corrupted by the zero-sum hypercompetitive nature of this process. Now it's just another way to game this ridiculous system. Here's my theory about what happened.
ADCOMs thought "it's a long process and we get that circumstances could change after sending in your application, so we should allow people to inform us if something important changes." They wanted only "meaningful" things like getting a paper published, getting some kind of prestigious award, etc. They expected that this would be a fairly rare occurrence, and so when they got updates they would read them and give the applicant a boost (an II, an acceptance post-interview, whatever).
Some people started pushing the envelope of what it meant to have a meaningful update, adding things like new jobs, new grades. Some schools appreciated these updates as well and would give those applicants a little boost. On reddit and SDN, premeds saw others benefiting from sending updates, and realized "this is a lever I can pull to influence the outcome of my application." They started to flood schools with updates about things like starting a new volunteer position, a few new volunteer hours, a few more research hours, using it as an opportunity to send an extra "Why This School" secondary essay. Some schools still appreciated these because it showed "continued interest." It became completely zero-sum, and applicants bad at playing the update game may now be at an actual disadvantage.
At some schools, ADCOMs saw this, and decided "screw this, we're not reading updates anymore." They leave the option to update on their portals because it's too much of a pain to change, and maybe once in a blue moon an applicant might send in an update that's really meaningful. At other schools that "appreciate updates," the game is still as zero-sum as ever.
