It is a requirement for the Gold Seal. Which is primarily a marketing tool. Once you have it, you always have it so it begs the question - what if your pass rate goes to 25%? I've had once since 1991 and have not trained more than 8 in a year since 2000.

I paid the money to get the AGI and IGI because the school I was training at was going to pay me to teach groundschool while I worked on my CFI/CFII so for me the $150 was a good investment (offer was 50% of the tuition from as many students as I could get in class - I typically had 8 to 10).

As a professional instructor - and yes you can make money at it by charging the right fees and getting the right clients - it may be worthwhile to have the AGI/IGI. Better credential is the master CFI which is much harder to get and keep as it must be renewed every two years. Again, these are for "professional instructors" not those seeking a career elsewhere.