Why should an API return 'void'?

Question

When writing an API or reusable object, is there any technical reason why all method calls that return \'void\' shouldn\'t just return \'this\' (*this in C++)?

For examp

Answer 1

Methods that return void state more clearly that they have side effects. The ones that return the modified result are supposed to have no side effects, including modifying the original input. Making a method return void implies that it changes its input or some other internal state of the API.