Unfortunately, what happens with explicit assignment is programmers often enough will:

1. just insert '= 0;' to get it to compile

2. insert '= 0;' and then be puzzled by an initialization further along in the code

3. see the '= 0;' and wonder why the programmer did that as 0 was not a valid value for it

A goal of D is to be able to make code more understandable. Forcing a vacuous initialization on the programmer is not conducive to that.