"Why"is a question that should be made to cisco developers and managers, but they are not here to reply it.
What I can tell you, is that if you want to do things professionally, leave SDM alone that beside not doing what you need, will produce confusing configuration and prevent you from learning.
Once you have learned how to make neat, clean and efficient IOS configs, you won't regret the SDM anymore, and on your route to be a Professional.
