They aren’t. 99% of what you do could be replicated by a fairly stupid shell script.
When I started as a DBA, I didn’t have practical experience as a DBA. I had Books Online and google.
What’s necessary as a DBA has nothing to do with your knowledge of T-SQL or SQL Server’s internal fiddly bits. That’s icing on the cake.
The skills necessary to become a DBA are things that we learn over time. These are the skills and traits that make us successful professionals, students, friends, and lovers. You need patience, inquisitiveness, and a healthy dose of skepticism. You should also be able to follow a checklist. Making the checklist is for the advanced class.
The technical skills of a DBA are the same as those of a plumber – they’re both skilled trades. There are varying degrees of success and skill. You can distinguish between the skilled and unskilled very quickly by their approach to life and learning. People who are good at their job possess the skill of learning: their practical job skills themselves are secondary to their ability to learn.