In the Sveshnikov variation, Black concedes positional advantages (weak pawn in d6, and outpost in d5) for dynamical play based on: active pieces, pawn break (...f5) and dark-square play. Indeed, White gives up their black square bishop early in the game meaning that they may lack of pieces controlling black squares.
It seems not appealing to exchange the strong d5 knight against the bad bishop in f6, therefore White usually develops a classical strategy in this case: put all your pawns on the colour of the missing bishop, i.e. White will try to put pawns on black square to control some black squares and then compensate their missing bishop.
In the position you point out Black has played two other alternative moves in practice: 12...Rb8 and 12...Bb7 and against both the strongest for White is 13.h4! (scoring very well in practice).
Why White does not play 12.h4 ? Well, White need to take care of two goals: firm control of the d5 square (otherwise they have no advantage) and fight for the dark square.
In case of 12.h4, Black has time to fight for the d5 square :
12.h4 Be6! 13.Nc2 Bxd5 14.Qxd5 Ne7 15.Qd3 d5! (and the d5 square and the d6 pawn are no longer a weakness).
Something similar may happen in case of 12.Nxf6, then for instance this could follow:
12.Nxf6 Qxf6 13.Nc2 Bb7 14.Ne3 Ne7 and 15...Rd8, 16...d5 cannot be prevented.