Quite a few reasons. Originally, I was stuck on .net 2 (.net 3.5 had only just come out), so LINQ wasn't available. Then, for a long time, LINQ to SQL was not thread safe. It doesn't generate stored procedures, so there is a significant network overhead for complex queries and complex queries can't be shared across language independent projects. And finally, my system provides a ton of metadata that I could then start leveraging for script generation. Entity Framework was too all-or-nothing, and my own system had too much momentum for me by that point. It has evolved over time and it has always just been easier to adapt it than to take on whatever has been popular at the time.