Perhaps the needs in enterprise are slightly different. Handling HA , backup and security! in a typical deployment entire DB is a single file on the application

Perhaps the needs in enterprise are slightly different. Handling HA , backup and security! in a typical deployment entire DB is a single file on the application runtime, in a multi-user context this is significant risk, basically you are trusting each app developers and admins to made the environment and code secure for each as opposed to centralized DB admins doing it. It is easier for a existing DB service stack when you are just adding one more DB, than handling DBs distributed across hundreds of applications typical in any organization. Managed SQL services for SQL variants are readily available and fairly affordable for applications which do not have access to such shared service layers . It does not mean that SQLite has no place I love using it in native applications and mobile apps, however multi-user web applications is perhaps not one of them, even concurrency is not a problem