Because some find it very annoying
Starting with Windows 7, Microsoft added Aero Snap, a part of the Aero Desktop experience not found in Windows Vista’s Aero Desktop. With Aero Snap, users can drag any window to the top, left, or right side of the screen to maximize the window in a special way.
Dragging a window to the top maximizes the window to full screen while dragging it either left or right maximizes the window to half screen depending on the side to which you drag it. Although useful for when you want to see two windows at the same time, some users find that the Aero Snap feature is a bit too aggressive, maximizing windows when the user did not intend to.
Luckily, Microsoft lets you stop the Aero Snap feature from operating without having to disable Aero Desktop altogether or making some complicated Registry entry.
Disable the Aero Snap Feature in Windows 7/8/10
To disable the Aero Snap feature, begin by clicking on Start and then entering Ease of Access Center into the Search Programs and Files search box. Press Enter.
Not surprisingly, you should now be looking at the Ease of Access Center, which is a central location for all ease of access options available in Windows 7/8/10. At the bottom of the list is an option titled Make it Easier to Focus on Tasks. Click on this option and you will be looking at the Make it Easier to Focus on Tasks window.
Near the bottom of the window, you will see an option titled Make it Easier to Manage Windows. Under this option, check the box titled Prevent Windows from Being Automatically Arranged When Moved to the Edge of the Screen.
Oddly, Microsoft didn’t just call this option Disable Aero Snap like it probably should have. Doing so would have made finding and disabling this feature a whole lot easier.
Why Disable Windows 7/8/10 Aero Snap?
Although a seemingly useful feature, some users find the implementation of Aero Snap more of an annoyance than a helpful feature. Users of previous versions of Windows could arrange two windows side by side by right clicking on the taskbar and choosing a menu option. Unfortunately, this method was frustrating when users had more than two windows minimized to the taskbar.
If you often have multiple applications open such as Word and Excel while you work, you probably spend a lot of time moving windows around to see what going on. Often, this includes moving a window partially off the desktop to view what’s underneath.
This is usually faster than minimizing the window to the taskbar for just a few seconds before having to restore the window again. With Aero Snap enabled, many users find that this feature actually slows them down when they accidently move a window too far to the top, left, or right of the screen. Enjoy!