I work as a freelance developer (mainly .NET at the moment) so a large part of of that decision is taken away from me as it lies with my clients. Arguable, I agree to take on work that includes SQL Server elements, however, like many I have worked with Oracle, DB2 and various other database technologies (RDBMS and otherwise).
I prefer to work with SQL Server over the other technologies because I enjoy working on a well integrated stack that in the large part "just works" (troll away). There is plenty for me to remember and learn with each contract that to cover too many database technologies might be spreading myself too thinly and would be a disservice to my clients. I like the commonalities across the toolsets. It is also easier to switch between different versions of the same product compared to also having to switch between different products.
How did I get into SQL Server? As a Windows C++ developer I took on a role that required development against SQL Server 7. I had already received a theoretical relational database education so it was about learning the tools and, most importantly, where practice differs from theory. Fortunately, I was working with an experienced DBA who was also a very nice chap. He ripped apart my first database schema design (in part) and pieced it back together in a review in front of me and others BUT he explained why. The review of the next schema I designed was far simpler for him and far more satisfying for me. Clever as well as nice, eh?
As for SQLServerCentral.com, well I could say that I gravitate to fellow reprobates but seriously I had an issue (cannot remember what, why or for whom) and found knowledge here both in the form of articles and from fellow professionals. I love the lighthearted approach of most allowing scathing debates without it becoming personal - although it must be said that sometimes Steve does step in to stop it going too far.
-- Stop your grinnin' and drop your linen...they're everywhere!!!