Forcing a favourable exchange on g3, which will clear the f-file for the rook and hamper Black's potential attack.

Preventing 4...Bd7 and enabling ideas like Rc1-c7 and Nd4-e6.

Intending ...Be5 and ...f5-f4 – Piskov.

With a sound extra pawn, whereas Black hasn't achieved ...f5-f4.

Inviting an exchange on d6, after which the doubled d-pawns would prove useful in taking the c5 and e5 squares away from the enemy pieces.
1...Nf4?! 2.Bxf8 Rxf8 3.Nc5 with some advantage for White thanks to his excellent knight.

Now that c5 is no longer available, the destiny of this knight has become less evident.

Limiting the rook on e3.

Securing the queenside pawns with a roughly equal game.

Preparing c4-c5 and c3-c4 in order to clear the long diagonal, even at the cost of a pawn.