100 dives is a lot of dives for a recreational diver. Most divers don't ever get close to that number. You need a variety of dives in different locations and conditions to gain confidence and experience.
If the goal is to become an instructor 100 dives seems to be the norm and seems to be working... but I personally think that 100 dives as a divemaster (divecon) with students should be required before you go to instructor. Students always find unique ways to surprise you in a class and the more experience that you have anticipating and dealing with these events the better off you and your students will be. Experience with students will make you an instructor that is much better equipped to handle whatever the students might throw at you.
If the goal is to become an instructor 100 dives seems to be the norm and seems to be working... but I personally think that 100 dives as a divemaster (divecon) with students should be required before you go to instructor. Students always find unique ways to surprise you in a class and the more experience that you have anticipating and dealing with these events the better off you and your students will be. Experience with students will make you an instructor that is much better equipped to handle whatever the students might throw at you.