The more you carry, the fewer places there are to think out loud.
Almost every conversation has a purpose attached to it. A decision to make, a position to defend, a team to lead, a client to keep. Even the people you trust arrive with a history, a perspective and a stake in what happens next, so you get very good at thinking for the room. And if you are building something on your own, there is often no room at all, which turns out to be a version of the same problem.
Sometimes what you need is somewhere to think before you know what you think. I work with people who want one hour to do exactly that.