Things have changed over the years. I, too, soloed in a short period of time (9 hours) and had my license in a total of 42 hours (including check ride). This was almost 40 years ago. Now there are so many aspects of flying that not only do you need to know but need to demonstrate before a good instructor will endorse a student to solo. Before all you needed to be able to do is go around the pattern to be endorsed to solo. After you soloed then you learned the other aspects of flying. Now there are the different maneuvers that need to be demonstrated, different knowledge of stall, recoveries, entry of patterns (controlled and uncontrolled airports), radio procedures etc., it goes on and on. All in all the time invested in this gaining of knowledge and skill is well worth the time and effort for the student and the instructor. It is not unreasonable for a student to aquire 20-25 hours of duel before solo.
Hawk