I have no idea if fracking causes earthquakes, but pumping s*** into the ground can't be a good idea. Energy consumption is a balancing act between what we can afford to pay versus what we can can afford do to the environment. People want cheap gas.
To the extent of my knowledge, fracking has never been shown to cause earthquakes, but pumping large volumes of liquids into known faults can cause the release of some of the pent up stress, triggering earthquakes, albeit usually relatively minor ones.
Nothing is ever black and white simple, oil and gas production from many formations invariably results in unwanted produced water. Something must be done with this water and it usually contains too much "stuff" to be safely allowed to drain into a watershed. When treating costs to make the water safe are higher than the cost to pump it back into the ground that it just came out of, and the laws allow it, then it probably will be disposed of with the least costly method available, ie pumping it into the ground.
I doubt that very many folks prefer expensive gas