Explain bed joint reinforcement to me

[flanagaj]

I am trying to understand why you install bed joint reinforcement in the 2nd/3rd courses of brickwork above a window and door opening when you will have a lintel that is going to provide the lateral strength and stop the brickwork from bending inwards?  Keen to understand why that thought process is obviously wrong.

[Mr Punter]

It is to strengthen the brickwork. Try demolishing a wall with brick reinforcement and you will see. A bit like reinforced concrete v not.