The idea
If players keep playing their strongest openings all the time and play several hundred of games per month, games sometimes become a bit boring, as the only time to think is between move 30 and 50. If you play some random moves early on, chances are high that your opponent can take the advantage to beat you badly.
So it would be nice to have a position early in the game which neither of the players actually has played plenty of times and that's almost even. In online games you could sometimes find top players who varied early knowing that their opponent will also try to play a random move to get into an almost even position. But this "even" is very subjective and frequently it turns out that the position was not really even after all.