The large wattage resistors are being used for current/voltage reduction, usually part of the excitation/regulation scheme.
It's easier (in design and production) than trying to get the windings just the right resistance, and in some cases can provide a means of adjustment.
In modern designs, these are replaced by high frequency switching and small inductances. So smaller but subject to the frailties of semiconductors when cost pressures reduce safety margins for power, heatsinking, noise/spike immunity (EMC).