- Is there any need to drag the window around? No, because you cannot actually drag a maximised window without restoring it, which can be done using the restore button.
So an extra click for zero benefit? In most WMs, MS Windows included, dragging a maximized window will restore it and start dragging all in one go. You also have the ability to drag it to another monitor, or to drag it to the far left or right to "maximize" it to half the monitor. Sure, most of these can be done with keyboard shortcuts, but so can switching between tabs.
There must be more to life than having everything. -- Maurice Sendak