Why is simple, it's in pursuit of improving the language, just like anything else. And while the bloat and increasing effort to keep up with new developments are obvious downsides, C++ has definitely benefited from the fact that it is a moving target overall. C++11 move semantics for example can help eliminate unnecessary copies and some class of memory errors (when dealing with non-copyable things)
C++ and C have both been around for ages. When they first arrived, most (all?) computers were single threaded and therefore neither of them put threading utilities in the standard library and in updates to both languages, now C and C++ both have libraries for dealing with multiple threads (and I believe an improved memory model that takes threading into account.)
Almost all programming languages evolve over time. Programming changes, computers change, and people gain experience and figure out what the pain points are in a given language. Naturally, we take what we learn and apply it to future language versions.
C++ and C have both been around for ages. When they first arrived, most (all?) computers were single threaded and therefore neither of them put threading utilities in the standard library and in updates to both languages, now C and C++ both have libraries for dealing with multiple threads (and I believe an improved memory model that takes threading into account.)
Almost all programming languages evolve over time. Programming changes, computers change, and people gain experience and figure out what the pain points are in a given language. Naturally, we take what we learn and apply it to future language versions.