What are the advantages of using electrical systems as a alternative to pneumatic systems in the Boeing 787-9? Is it a maintenance advantage?
Just on example: The energy taken from the engine as bleed air is contained in this bleed air as heat and as pressure. Now pipe this energy to someplace where it is needed, and the air will cool down and lose some of its pressure. Also, if you want adequate insulation and low transmission losses, the cross section for the piping will be substantial.
Compare this to taking the energy from the engine by a driveshaft turning a generator: Friction losses will be a few percent at most, energy conversion in the generator will be at above 90%, and transmission losses are low again if your cable cross section is sufficient. Note that the cables will be much thinner than any bleed air line would ever be.
Add to this the advances made in converting electrical energy between different voltages and frequencies, and it becomes clear that modern aircraft systems can be made more efficient when run electrically. The use of compressed, hot air was only a better choice when modern power electronics were not yet around.