This is just a personal opinion. But as apps scale you run into concurrency problems. You want to maintain a reliable consistent state but due to latency and

This is just a personal opinion. But as apps scale you run into concurrency problems. You want to maintain a reliable consistent state but due to latency and resource limits that is difficult to do within your own code. So the responsibility is moved onto another system designed for that purpose. NoSQL simply solves the same problem in a slightly different way. The consistent state is allowed to be abstract and doesn't need to be transactional. The real dichotomy is between handling state yourself in code and letting outside software do it for you.