why does simulink use the transfer function to simulate the step response?

[Aditya Adhikary]

Both of these are separate blocks. Simulink does not "use" the transfer function, the model which you have designed or referred to here passes the output of the step function to the transfer function.

[Giuseppe Alfieri]

I'm sorry but i didn't explain myself well. My question was because the output of transfer function's block is the step response in the time domain and not in Laplace one?