An inductor tends to maintain its present value of current. When a current is established in an inductor, then a switch is activated forcing the current to change paths, the current does not change abrupltly when the terminal impedance is changed. The voltage abruptly changes. Switching power supplies work in this manner.
A typical electrical generator can output constant current or constant voltage. Forcing the generator at constant speed results in constant voltage. Forcing constant torque results in constant current. An added benefit of constant speed/voltage is constant frequency as well. This makes synchronous devices feasible, like clocks, or phonographs.
A battery can be produced for constant current operation, but constant voltage works better. However, nuclear batteries tend to be optimized to produce constant current.
Current sources are not produced for a good reason. Conduction losses are greater than insulation losses because insulators approach the ideal better than conductors. When turning on a lamp, the wire has a conduction loss due to resistance, and an insulation loss due to leakage in the insulator. But the conduction loss is much greater.
The power grid is constant voltage because it results in much lower losses. A constant current power grid would mean that full current is always being generated and distributed. To turn a device on, we would open a switch in parallel with the device, and a voltage would develop.
This would be very lossy. If high temperature superconductors ever become available and cheap, this might happen. For now, constant voltage is way better and all batteries, and generators will be designed as such.
Does this help?
Claude