I see that most of the apps that include heavy GUI content are usually developed in C++. Most of the games/browsers are coded in C++. 

Can't we just develop better GUI apps with the latest dynamic languages? I know java wouldn't be a great choice. But what about languages like python which are natively built on C? Aren't the latest languages supposed to be better than their ancestors? Why do we still have to prefer the age old C++ over the latest languages? 

And I would also like to know, what is it that is responsible in C++, for the better speed of processing GUI? On the other hand what is it that the other latest languages lack? 

I'm one of those people who write C++ GUI apps (mostly for windows). With Qt, to be precise. My reasons:


I like C++. I'm a freelancer and usually I can choose my tools (lucky me!)
In a managed environment you may have a hard time when you need to use some unmanaged code (long-winded WinAPI declarations in C#, anyone?)
Fewer dependencies that are more easily deployed
More control over everything. 
RAII (vs. GC). And even if I allocate with new, I rarely ever delete anything explicitly, because I use smart pointers or the QObject hierarchy.
C++ is very exciting these days, I can't wait for a compiler to fully support the new standard.
Speed (only at the end of the list. I know it's not that important for the GUI itself, but it tends to be speedier because C++ programs don't suffer from the overhead that runtimes, byte code JIT-compiling and similar technologies add to the program.)


As you can see, these are mostly personal preferences. I find it important for my work to be enjoyable and C++ provides that to me.
