Zwischenzug Question

In doing thousands of tactical puzzles on this site it appears to me that if there is the opportunity to make an easy capture while at the same time an opportunity to safely check the King, it's the checking of the opponent's King that is almost always the correct move to make, prior to the piece capture, even if checking the King seems to reap no obvious or immediate benefit--it often appears to do nothing more than force the King to move over a square before losing material in the following move. 

What am I missing? What is the benefit of the Zwischenzug tactic in these particular cases that I'm not understanding?

Thank you

zwischznug is basically an in between move 

and you gain the initiative and a king of h1 or g1 can make a big difference at one point