First of all, I think that you need to understand a bunch of concepts in order to answer your question:
All digital designers use the name flip-flop for a sequential device that normally samples its inputs and changes its,outputs only at times determined by a clocking signal. On the other hand, most digital designers use the name latch for a sequential device that watches all of its inputs continuously and changes its outputs at any time, independent of a clocking signal. However, 'some textbooks and digital designers may (incorrectly) use the name "flip-flop" for a device that we call a 'latch." In any case, because the functional behaviors of latches and flip-flops are quite different, it is important for the logic designer to know which type is being used in a design, either from the device's part number (e.g., 74x374 vs. 74x373) or from other contextual information.
Regarding to what you have asked, S-R latches are useful in ''control" applications, where we may have independent conditions for setting and resetting a control bit. If the control bit is supposed to be changed only at certain times with respect to a clock signal, then we need an S-R flip-flop that, like a D flip-flop, changes its outputs only on a certain edge of the clock signal.
You can get a master/slave S-R flip flop by using two S-R latches.
The logic symbol for the master slave S-R flip- flop does not use a dynamic-input indicator, because the flip-flop is not truly edge triggered. It is more like a latch that follows its input during the entire interval that C is 1 but changes its output to reflect the final latched value only when C goes to 0. In the symbol, a postponed-output indicator indicates that the postponed-output signal does not change until enable input C is negated. Flip-flops with this indicator kind of behavior are sometimes called pulse-triggered flip-flops.