The main menu should be important to the developers of any game. After the opening sequence it is the first thing that the players see. It is also the part of the game that the player will most likely see the most. It is the main hub for navigating the game. First impressions matter and that is why taking the time to make a main menu look nice can help the overall reception of a game. Having a bland main menu is an opportunity missed to impress the players.
Example:
The Dark souls games are amazing but their menu screens are very boring and are not intuitive. These menus are not a great demonstration of how technically brilliant the game is. If the player bases their opinion of the game off of these menus they will be unimpressed and unwilling to push through these difficult games.