SRE here. Most of time we see choices like this because teams are under pressure to deliver and scale would likely exceed what a database will easily handle with the out of the box settings. So tweaking is required and that takes time/knowledge that Dev team doesn't have. AI helps a bit here but it didn't exist when DynamoDB solution was chosen. However, some terraform, and boom, scalable database created, only downside is the cost which is next Product Manager problem.