Several years ago I worked with an ex-Microsofter who'd worked on the NT kernel and SQL Server. There were several times when I asked him why so-and-so was so awful, and his response was always that they didn't have the good people working on it, because they were all working on NT and SQL Server. My response was that as big as Microsoft is, they should have enough good people to go around.

Really, I'm convinced it's not the average engineers in the trenches who make the products so horrible, but management and marketing's influence over management that causes everything to be a trainwreck.