En passant

Why would you constantly try that? Just do it when it's a good move

I don't get much opportunity to do en passant

If you're a beginner playing other beginners, you might do it to show off your in-depth knowledge of one of the obscure rules.   I can't see much advantage to always go e.p. after that.

On those very early "chess challenger" computers and programs, I used to routinely create e.p. opportunities just to "tempt" the software. My experience was that they always made the e.p. capture. Not surprising, as the programmer would want to show that his program had this capability. To prove this, however, I'd have to set up a situation wherein it ignored a certifiably *better* move, and I wasn't this motivated.

Speaking about en passant.  

I wonder why so many people still are surprised or don’t know about that move. Even players who played for longer time.

Is it because they learned chess from another human? 

Because I learned it online and from chess.com, en passant is practically one of the first things I learned.

The only time you need to do the en passant move is if your opponent's pawn is a chicken. 

yeah it's not always the best move but sometimes when it is then it can win a game