Performance Tuning with SQL Server Dynamic Management Views

Dynamic Management Views (DMVs) are a significant and valuable addition to the DBA's troubleshooting armory, laying bare previously unavailable information regarding the under-the-covers activity of your database sessions and transactions.

Why, then, aren't all DBAs using them? Why do many DBAs continue to ignore them in favour of "tried and trusted" tools such as sp_who2, DBCC OPENTRAN, and so on, or make do with the "ready made" reports built into SSMS? Why do even those that do use the DM...