The main issue with lithium sulphur is cost. The tech exists and has been used in several projects but commercialisation firmly remains a longer term achievement and in that time existing lithium battery is improving in efficiency and design and cost point.
Existing lithium ion batteries also carry the advantage of being simpler to produce and battle tested. They have faults, sure, but the faults are known - it takes time for the unknown unknowns to be ironed out of any new tech.
I think the other competing tech to existing lithium batteries is vanadium redox, which is doing well in the fixed facility mass storage space.
