For single thread performance.
This can equate to a faster chip because you now can do more at once. However, we hit the frequency limits a while ago for silicon. Particularly, parasitic capacitance is a huge limiting factor. A capacitor will start to act like a short circuit the faster your clock is.
Moore's law has a little more life, although the rate seems to have slowed. However, at the end of the day it can't go one forever you can only make something so small. One gets to a point they have so few atoms to constructing something useful becomes impossible. Like current transistors are finFETs because the third dimension gives them more atoms to reduce leakage current, compared to the relatively planar designs on older process nodes. However, these finFets still take up less area on a die.
Moore's law does help with efficiency to some degree, small transistors generally require less power to switch. However, most the power is last due to the miles of wiring in a modern chip when running at such high clock cycles. Again, it's the parasitic capacitance.