At higher levels, moving your queen that early isn’t a good idea. At beginner level, the 4 move checkmate can boost your rating so you get better opponents.
Dont rely on opening traps too much, but play in to a strong position with alot of plans for attacking. But you still need to be able to defend if needed
The 4 moves one is called Scholars Mate and yep it's pretty easy and useful because even if we can't checkmate we can still win a rook and have a better position.