What needs or works better with DC than with AC electric?
TVs, PCs and LED bulbs all run off varying DC voltage, although you'll find interestingly enough that the most efficient DC->DC converters are actually DC->AC->DC converters. (See resonant converter)

I'll expand a bit more on the motor front. AC induction motors (that run directly off AC mains) have been the standard industrial power source for many many years. They are cheap and very reliable. A large portion of the electricity generated (see below) is used to drive a AC induction motor in one form or another (as a water pump, air pump, conveyor belt and so on). Newer more efficient AC synchronous motors (being used in some electric cars, washing machines and more), have variable-frequency inverters inside them anyway, and so can be fed with AC (which is rectified) or DC with minimal loss in efficiency. DC motors are usually much smaller than both these types by comparison, and even then, they are often used with pulse-width modulated (PWM) drives which would rectify any AC before adjusting the voltage.

Induction motor usage stats:
30% of total energy (according to http://www.mpoweruk.com/motorsac.htm)

80% of total mechanical energy (according to http://electrical4u.com/construction-of-three-phase-induction-motor). 
No actual studies provided by these sites though.

I found some similar questions

Why is high voltage AC more common than high voltage DC?

Why are the power transmission/distribution systems AC and not DC?

Neophyte question about AC vs. DC (especially for powering a home)