bishop b5 is the most annoying play you can do.

so many times I will have a free pawn lined up with my knight, then BOOM! my knight is pinned to my queen. I now have to either kick the bishop, losing tempo, or give up a valuable knight or queen. i even have times that people bishop to b5 for NO REASON. Even if there's a pawn between the queen and bishop, they STILL DO IT, knowing that it's just going to get kicked and possibly lost. why do people do this? even in most of the analyses, it says it is an inaccuracy. Still, in almost every game, somewhere along the line, my opponent plays bishop b5. why? why is it so popular? what can i do to counter it before it happens? 

Can you post a game when it happened?