Plus some people don't know when to ask for help, or when they're (for instance) duplicating effort.
Informal gatherings are not an appropriate venue - if this stuff only comes up then, then lunch gatherings are now work, and they're mandatory.
This is the gist of it. Some people just have this (very sincere) belief that everyone else are clueless idiots and need to be nurtured, protected and helped. This is the spirit of our age, and Scrum in particular is just another manifestation of this belief.
If you have a small(ish) team of great people you can get a lot done with a very informal process. When you start to grow, or you're not necessarily hiring the best there are, you start to need this stuff.
And you don't always need the self-motivated, highly productive builders. Someone has to make small tweaks, pad out the automated test cases, maintain things, document etc etc.