Scrambling 2NT

The scrambling 2NT bid is used after partner makes a takeout double at the two level, and you hold two four  card suits.  E.g.  (1S)-p-(2S)-x; p- ??? and you hold:  S: Kxx H: Qxxx D: Jxxx C: xx.  If you bid hearts, you could wind up in a 4-3 fit (and the same with bidding diamonds).  Why guess? If you bid 2NT as a scramble, partner can bid his four card suits up the line.  With S: xx H : Kxxx D: AKx C: QJxx , partner bids 3C over which you bid 3D to deny holding four clubs and then partner bids 3H to  show that suit.  Why play this convention?