I think people become dive instructors for one of 3 reasons....
1. They love diving, and having enjoyed the hobby for an extended period. They wish to pass on their knowledge and open the doors to the underwater world to other people. It is also a career that enables them to get into the water every day.
2. They see the instructor status as the highest pinnacle in diving and are inspired to race towards having that certification to validate a self-belief in their superior skills underwater.
3. They want to live and work on a beach/in the tropics... and becoming a diving instructor is easily accessible, in a short timescale, with some financial investment.... and it will fund a better lifestyle than a bar job.
So, who should become a dive instructor?
For me, it should only be people in the first category. Do I need to explain why?
People in the second category are, IMHO, very off-the-mark. Being a dive instructor is easy... and it certainly does not represent any sort of pinnacle of achievement.These people would be better served persuing training in technical diving.... which stresses a much higher standard of pure dive skill and application. For less money than an IDC, a diver can undertake several tech classes, or Fundies etc. They will be much better off for it and be held in higher regard and respect also.
Lastly, those people in the third category represent a cancer in the dive industry. IMHO. They have no passion for diving. They have no background in serious diving. They don't care (or even understand) how or why they should be educating safe, effective divers. They provide the bare minimum required on courses (or even fail to meet the minimums) and are more concerned with drinking, partying and shagging. They typically only stay in the industry for a year or two...before burning out and returning home to finish their college degree or get a 'proper' job. They work for peanuts and serve to undermine the earning potential, respect and credibility of real 'dive professionals'.