Why we do notate this way?

I'm a big fan of algebraic notation, its a very simple way of recording games. But there are flaws, such as in this case:

Notice that the last move played was recorded as Nge7.  But this is inefficient, as there was only one knight that could legally move to e7. Therefore the move should just be written as Ne7. 

Just guessing but it was probably just quicker (less comlpicated) to program it to notate that way and not throw in a check to see if the other option was or wasn't legal.

One of the programs I use does the same thing (probably more do but I haven't checked).

I'd write Nd7 there. If I'm not wrong, Chessmaster used to do it in that way (that's the only chess program I've ever used). Also, when "touching" a piece that had only one legal move, it made it automatically.