Primarily due lack of a sufficiently cheap and convenient high energy density storage... though we are getting closer now with all the modern research on batteries thanks to the economic incentive to power ever thinner and power hungry smartphones.

On the energy generation side, it's taken pretty advanced tech to get efficiencies upto acceptable levels in Solar and Wind.

Nuclear unfortunately has proven to have drastic fast acting negative externalities on failure (mass evacuation, increase in cancer rates) and tbe Industry has consistently shown lack of competence in preventing failure. So it's no surprise people have soured on it.

Given the trajectory of tech development, I'm fairly confident we'll get there - hopefully before we screw up our climate too much.