There are different mindsets for DBAs and database developers. There's stuff they share, and stuff that one can learn from the other. It's folly to assume DBAs are going to think like database developers or database developers are going to think like DBAs.
All this means, in this context, is: People in our field are going to react differently to the idea of test-driven database development.
Regarding Team System: If you've been working with SQL Server for a while, you can see a pattern in the tools emerging. If you worked with DTS in SQL Server 2000, you did that in Enterprise Manager - the same place you did a lot of enterprise DBA tasks. With SQL Server 2005 came SSIS, and along with it a version of Visual Studio for developing SSIS.
Can you do SSIS development inside SQL Server Management Studio? Yes - and you do, in fact, whenever you create a Maintenance Plan. So if it's possible inside there, why not leave it all there?
My thinking is Microsoft is attempting to sever purely development activities from administrative activities. If I was a betting man, I'd bet the trend will continue. If that bugs you, you may be bugged.
Database Edition is free with Developer Edition as of October 2008. A full Team System license isn't required unless you're wanting to do other Team System stuff (and then it's justified for those reasons).
As for source control, you may not like it - many do not - but it's a reality for most database and application developers. Beyond the legal / auditing requirements, source control is just a good idea. I doubt seriously you'd question the assertion you should backup your database. One (merely one) benefit of source control is it backs up your business logic.