Why a quantum computer simulation is not a quantum computer? Is it because the inability to generate true random numbers  (I dont think so) in the host machine or something else?
My understanding is that the ability to emulate a quantum computer in a conventional one would eliminate the need for a real physical quantum computer if we can emulate Qbits and superposition .
I know its not possible or very very very very difficult because researchers and companies are investing in real quantom computing but what is the real scientific reason. It seems google attempted that maybe because se from their perspective they have more programmers than physicists...     
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P. S. 
I used the terms simulation and emulation as different things so that the question reads "Why a Qbit simulatior is not an emulator" 
as in a Flight Simulator can be used to learn how to fly a plane but not to travel but  lets say a casio calculator emulator running in a digital pc can be used to calculate whatever a real casio calculator can achieve. 
 A: It is possible to simulate quantum computers with classical computers. However, the time (and typically memory) needed for such a simulation will scale exponentially with the time a quantum computer needs.  Thus, if a quantum computer needs $10$ times the computation time for a more complicated case, the simulation would need $2^{10}$ times more time, and so on.  Conversely speaking, we believe that a quantum computer can solve certain problems with exponentially less effort than a classical computer (including a classical simulation of a quantum computer). Thus, we want a quantum computer and not only a classical simulation of a quantum computer: It should ultimately be exponentially faster in solving certain problems.
A: The uses for quantum computers has two major sections: quantum algorithms and quantum networking. 
Quantum algorithms are algorithms for quantum computers which offer a significant speed improvement over classical versions. A famous example is Shor's algorithm which factors integers in polynomial time compared to the classical version which factors in exponential time. Quantum computers (and their algorithms) can certainly be simulated on a classical computer; they often are for development purposes. However, the current state of a quantum computer is a vector whose length is $2^n$ for $n$ qubits. Simulating, even storing that vector takes exponential time and space. A quantum state representing 64 qubits can be stored in a classical computer using (8 bytes * $2^{64}$) = 131,072 petabytes. Useful quantum algorithms may need thousands or millions of qubits. They cannot be simulated on a classical computer using exponential space.
Even if a method to simulate a quantum computer efficiently on a classical computer was found, it would not help the other major area of quantum networking. Quantum networking uses fundamental properties of quantum computers to ensure data is sent securely through the internet. A qubit's superposition collapses when measured and cannot be cloned. These two facts allow for secure data transmission guaranteed by the laws of physics themselves. A classical simulation of a quantum computer cannot replicate these properties so a quantum computer is required.
