In the games I have played, most of the capturing occurs on a venturing action. If you fail a venture action, that is roll a five or less after dice modifiers, the adventurer is captured. Yes, a combination of the right room with the right adventurer will never result in a capture, but my son recently captured seven of my adventures due to low dice rolls and bad match-ups.
Captures don't occur frequently during a scout action because those only happen when a 1 is rolled.
Thanks for answering my post. I just didn't understand the venturing rule. Now all is clear.