The view title on every view already has a menu with those choices.
Perhaps, but since there are already buttons on the interface, and generally speaking buttons are more fun to play with than menus, why not give those buttons a little bit more power and throw in the related list control functions as well? MC has always been the best at giving you different ways to accomplish the same task.
Part of the reason for asking for this, is that I have recommended MJ to a friend who uses itunes at the moment. I was thinking about how he'd find out about the different view methods. At the moment, (I assume the the list style buttons still aren't in the toolbars by defualt), he'd have to stumble on them through curiosity of what's in the drop down menu. Maybe that's fine for features like switching between panes and library view, but the list styles (to me) seem like the most fundamental of browsing methods. Thus, they need to be staring at you from the beginning.
And by extension, if those buttons were there from the beginning, and people were comfortable using them, their curiosity might just introduce them to the "Group by" features in a nice little drop down menu. This would be a gentler, less daunting, way of introducing MC's features than having one drop down menu with all the library view options, grouping options, sorting options, and list view options, staring out at you.