Obscure Rule Question: Is it Legal (or Beneficial) to Not Promote?

I'll start by admitting that I have not read the FIDE rulebook lately.  I'm hoping that someone here has or at least knows how to.  My question is twofold:

1.  Is it legal to advance your pawn to the eighth rank and not promote it to another piece?

2.  Legality aside, can anyone think of any scenario where it would be at all beneficial to have a pawn in the eighth rank instead of a piece?

Anyone?

No. A pawn moving to the eighth rank may not remain a pawn, and must promote to any piece of its own color, and may not promote to another King.

In the USCF's Official Rules of Chess (pg 15)

8F6. Pawn Promotion.  On reaching the last rank, a pawn must immediately be exchanged, as a part of the same move, for the player's choice of a queen, a rook, a bishop, or a knight of the same color as the pawn.  This exchange of the pawn for another piece is called promotion, and the effect of the new piece is immediate.  For instance, it may give check or serve to block a check.  The promotion piece is placed on the eighth-rank square to which the pawn was moved. 

By definition, the move is not complete until a promoted pawn is replaced, so the question of legality (using USCF rules) has been answered.

Regards,

Brian

3.7.3.3    When a player, having the move, plays a pawn to the rank furthest from its starting position, he/she must exchange that pawn as part of the same move for a new queen, rook, bishop or knight of the same colour on the intended square of arrival. This is called the square of ‘promotion’.

https://handbook.fide.com/chapter/E012023 

I don't think there is a position where it would be helpful. One of bishop and knight should also avoid a stalemate.

@5

Legal: no, beneficial: no.

Promotion used to be optional according to British rules, but they fell in line with FIDE.

Here would be beneficial.

Ah, nice!

Another position when not promoting is beneficial