One option is so called "virual ground" .. https://tangentsoft.net/elec/vgrounds.html
Without going into details, it is like dividing the input voltage into 2 identical halves ..
If, however, you need (or prefer) to keep the same ground as the input voltage, you will have to use a step-down voltage converter (linear od switching) to produce +12V and a dc-dc converter to generate -12V of +24V or of +12V ..
Its a cost saving issue. The system has 24v, 12v, -12v and 5v. Buying a powersupply with these is resonably expensive and Im sure theres way to just have a standard 24v supply and then have a small amount of analogue circuitry to supply the voltages.