Transportation Secretary Elaine Chao described the measure as a "safety" measure responding to the "unique challenges" of lithium-ion battery transportation. The FAA has pushed airlines to reconsider the transport of batteries because of the potential risk of fire, and the ban theoretically reduces the risk of an incident putting travelers at risk.
The freight ban will mainly affect those who order batteries. You will probably still receive your orders, but they may have to wait for specialized cargo flights. The requirement of charging the battery can be another problem. This could mark the end of the days when we received phones and other gadgets almost fully charged – you will probably need to recharge them beforehand.