It depends on how you want to use it I guess. It's about having a choice.

Each type of adaptor has its own strenghts and weaknesses. I've done tests where OLE DB was faster than ADO.NET.

Should I throw away performance because someone else wants to use the connection manager in an API? No, I want to have a choice.

Some components only work with OLE DB (lookup), some work only with ADO.NET (CDC). Some providers are only available in ODBC.