RDBMS have completely dominated in a way that few other technologies have. Especially for anything that might be described as business data (which is the prime

RDBMS have completely dominated in a way that few other technologies have. Especially for anything that might be described as business data (which is the prime value market for databases). Everything else is relegated to share a small niche. If you count SQLite as an RDBMS, the domination is even more complete. So, my question to you is: why? It can't be some kind of vendor lock-in, because there is no one vendor; there are several commercial vendors and open source projects available to choose from (each individual vendor might lock in their users, but that doesn't explain why they are still all RDBMSs and not something "better"). It can't be legacy, because SQL is as popular as ever; perhaps more so, as it seems that using a normal filesystem to store data is not very common any more. So you need to explain why they are so popular yet so wrong; otherwise it just sounds like a case of "everyone is dumb except me".