Why not encrypt/decrypt data in SQL Server directly instead ?

Right now I use Rick Strahls Business Object class... this project already exists on a .dbf backend... so the goal is to use the exact same code for both a .dbf backend and sql server backend... thus continuing the use of the existing encryption/decryption routines. That way... when I'm read to throw the switch on moving from the .dbf's to the SQL Server nothing else changes.

There seem to be a number of warnings when using SQL Server encryption... like it can be machine specific... it requires .net....

To be honest I'm completely open to it... just wanted to know best practices by others that are already doing it. Learn from other's mistakes :)