Earlier quoted context omitted.
I take a very cynical view of these things, and from that perspective it doesn't surprise me at all, really. My cynical view is that the "lousy" ones are popular because they are easy even for non-technical people to learn well enough to be useful in the majority of business settings. This sets up a kind of feedback loop: there is an abundant supply of "cheap" labor who can use these languages, which companies love,…
I think its more of the realization that types are actually freaking useful for determining "provability" of a system. C++ perhaps takes it too far with Const, but it allows the compiler to prove that certain functions will not attempt to modify certain variables. Compared to Python or Ruby, you're pretty much relying entirely on culture and good habits to ensure the proper rules of encapsulation. Any code may modify…
There is very little in terms of "provability" that either C++ or its types give you. Proving anything really interesting (for example, the absence of race conditions in concurrent code) still seems like pretty much an arduous process in languages not explicitly designed for such things.
Compared to Python or Ruby, you're pretty much relying entirely on culture and good habits to ensure the proper rules of encapsulation. Any code may modify the private members of your objects. (Granted, C++ has "mutable", Java has the whole "Reflection" loophole as well. But you can search for those edge cases rather easily).
That didn't seem very comprehensible to me, but if you're claiming that in Ruby, you can modify member variables of someone's objects, well, you can't, unless you use reflection as well (not only that, but the access to member variables is object-based, rather than class-based, so you can't access the member variables of an object from any other object, even if they are of the same class, unlike in C++ - so much for the "objects communicate by passing messages" in C++!). More to the point, in C++, you can always cast a pointer into something that makes the raw data accessible. There's enough stuff in C++ for you to blow your whole leg off instead of just shooting yourself into the foot.