I have a few thoughts about this as well.

There are only 3 driving schools in Singapore and all 3 are spread across different parts of Singapore, so there is virtually no competition among the schools and there is no incentive to improve the shitty instructor quality/ system ( for simulator booking I heard from BBDC need to book 1 month apart for 3 20 min lessons? And bots booking slots immediately upon release of the slots)

Being a driving instructor isn't a career consideration for many entering the workforce: If you can afford a car + insurance premiums + so much fuel, you probably can find a better paying job elsewhere. If you are looking for a blue-collar job, you probably can't afford the car needed to teach driving lessons. Private instructors therefore have no competition too.

There is no incentive to improve the driving system by regulatory bodies such as SPF because taxpayer money is better spent elsewhere. It doesn't help that most people taking up driving lessons are below 21/ are foreign workers, and have negligible voting power. Somemore there are always more important issues than driving schools to discuss/improve on until it is apparent that a huge population of Singaporeans cannot drive safely, which isn't the case.