My hair wants cutting.这里为什么要用cutting 而不用被动语态to be cut 或者being cut?

当主语是人时,want to do , 如 I want to go out. 当主要是物时,want doing ,如 The clothes want washing.want 的动名词形式本身就有被动含义.want doing 还可写成： want to be done所以,My hair wants cutting. =...