In the same way that a person who does datawarehouses I should know how to write great queries, consider the impact of indexes and be able to perform basic DBA tasks, I would beg to differ with you on the point of DBAs not needing to know at least the basics of data warehouse and BI implementations.

The reasons are many but not least:

1) Most DBAs will perform some BI tasks and doing any task well is what you should be aiming for

2) If there is a seperate BI team then understanding their requirements and typical tasks means that you can work with them better (or if you think they're like developers you might want to say manage them, herd them, lock them down etc)

3) Gives you an avenue for growth should you want it - being a DBA is a great job I'm sure you'll all agree but how many BI people are on call 247?