Understanding Block Diagram for Load Switch
The first triangle is a buffer followed by a level translator which will help in turning ON the P-channel MOSFET with control voltages much lesser than the voltage applied at the IN input pin. For example, you can use a 1.5V logic to turn ON a 5V load.

The second triangle seems to be a slew rate limiter which will help in linear ramp up of the output voltage so as to maintain inrush current limits in the circuit.

Now, I am not saying that these features cannot be accomplished with a discrete MOSFET circuit. But that will involve adding extra components to the drive circuit of your MOSFET. The SiP32431 device will provide you with a single-chip solution to accomplish all these requirements.