When you edit a cell in a table then press the enter key the selection box disappears. Then when you press the enter key again the selected row jumps to the first row in the table.
If you use tab instead of enter the selection box moves to the right allowing you to move through the table to continuing editing. If a table only has 1 or 2 columns out of 10 that are editable then tabbing through the entire row is very time consuming. For a user who is good with the ten key and only uses one hand for entry, the tab key is just too far away on the keyboard.