Attendees may leave a presentation better informed about a topic, but most presentations are unlikely to grant new skills to the audience. Training is, for the most part, a separate goal. Presentations are frequently one way communiques designed to generate thought or debate, or introduce a new tool or methodology. But, it's rare, even at B-sides events, for presentations alone to achieve the type of engagement that results in solutions and deep collaboration.
The excuse to bring people into narrow physical proximity generates some of this synergy in the form of "hallway con." And many argue this is the real value of conferences: a 'safe' forum in which like-minded people can have informal discussions off the books that result in ideas, agreements, or collaboration that more broadly influences or improves things.
In response to the solutions disconnect, some have proposed "hack-a-thons" in which talented individuals come together for a set period of time and a specific goal to program solutions. But, this approach is likely to alienate community members who don't code, and is more likely to hinder innovation across the lines between policy/process and tools manufacture/usage.