Why classes implicitly derive from only the Object Class?
This is only an answer to answer the question in the title.

Languages such as Java have every class deriving from Object for two reasons.

Firstly, to increase the amount of polymorphism available. This was particularly required before generics were added to the language. Without Object,  collection classes would be impossible to write in a useful fashion. 

Secondly, there are many methods that classes are expected to have or are useful, and these are collected in Object. By ensuring that all classes inherit from Object, all classes will implement  the same minimal interface.

As mentioned in a comment, C++ does not have a class like Object. C++ is in many ways untyped, so the issues I mention above are not applicable. Also, C++ templates provide a lot of polymorphism and are used to implement collections.