My last student soloed at 15.4 hours, and he was an exceptionally good student. Students under my tutelage don't solo until they are ready, and when there is absolute confidence on my part (if something happens, it's my metal getting bent). Striving for a quicker solo time shouldn't be part of a student's thinking, it can easily become a distraction that hinders progress. Safety should be the ultimate key and this required a long term approach.
All to often I see young instructors at the pilot factories pressured into soloing low time students, most of the time the students land without incidence, but not always. The NTSB reports are littered with initial solo accidents to proving it an unwise practice.