Some people come to conferences, where they see many short presentations. There is never time for more than a few minutes of discussion. Even in panel sessions, only a few minutes are spent by discussants on each other's opinions or data. Another problem at conferences is the promotion of credentials instead of the promotion of data. We're mindful of an article by Bill Hetzel on software metrics in which he complained of the difficulty of tracking down the data behind many claims.
Many people learn techniques from peers.
If you stay in one company, you all work your way into a common rut. Somehow you divine from them what people in the other companies that they've worked at do. If the consultant does a good job, you steal some ideas. If not, you reject the ideas along with the consultant. This is expensive and often ineffective.