Most applications rely on you selecting which text you want to cut, copy, or delete. Visual Studio makes the very simple assumption that if you have not selected any text that you want to cut, copy, or delete, the editing action will be performed on the entire current line. If you wanted to move one line below another line, you could move the cursor to the first line, press Ctrl-X (Edit.Cut) to cut the line, press the down arrow to move to the next line down, and then press Ctrl-V (Edit.Paste) to paste the entire line. Other shortcuts like Ctrl-C (Edit.Copy) and Ctrl-L (Edit.LineCut) follow this same rule and allow you to copy or delete the current line by simply pressing the shortcut keys without selecting any text. Any time you can avoid reaching for the mouse to select text is time saved.