The R-78Bxx-2.0 series is a high efficiency switching regulator. The efficiency up to 96% means that very little energy is wasted as heat. Full power is available over a temperature range of -40°C up to 70°C without the need for heat sinks with their additional space and mounting costs.
The input voltage of the batteries(7.2V) is used to power the H-bridge and the Motors. To use the controller and sensors, a 5V input is needed. So a step down to 5V is necessary.
The LED strip approximately uses more that 2A for the 72 LED's. To devide the current 2 voltage deviders are used to power the LED.
At first the AN7805 DC DC step down was used to have a 5V regulator that has the possibility to regulate until 1A. But the efficiency was much lower and there was a lot of energy going into heat. So a heat sink is needed to use the AN7805.