Some of the reasons I suspect, you will never find a true, elementary, step-by-step approach are as follows:
1) the sheer level of complexity of creating/producing music using virtual instruments, notation programs, and daws, along with the infinite variety/combination of tools an individual will use, make it difficult to create an organized tutorial from beginning to end that would be relevant to a large number of users.
2) a lot of the learning happens from using/making mistakes and creating "building blocks of information" so that over time, you figure out what to do more efficiently/effectively; avoiding these steps may seem desirable, but ultimately the greatest learning happens from experiencing the process, mistakes and all.
3) those users with great expertise are likely busy creating music and lack the time/desire to go back and create a helpful learning guide for those just starting out on their journey. Further to this, experts often lack the educational background to break down or chunk information in such a way as to effectively teach it to newbies. They may make suppositions or take for granted what they believe is common knowledge, leaving important steps out of the process (this has often happened with tutorials I've viewed, in which the instructor left out "in between" steps because they are so familiar with doing something that they assumed everyone would know "where to click" for example). At the other end, some tutorials are wayyy to methodical and slow paced, repeating ad naseum, the same information to the point where you feel like they're speaking to five year olds.
4) this one is a reality that nobody outright admits, but is a fact (in my opinion); composers are in a highly competitive field and will not divulge the knowledge necessary to compete with them. It would be like KFC telling you their 11 herbs and spices. Furthermore, many artists are insecure both with their skills and their process, and don't want to subject their ideas to criticism or scrutiny by those that might attack the way they do things as being inferior.
5) the financial incentive just isn't there to develop such a methodical guide, in a world where people will "take, take, take" and maybe at most give you a "thanks for the info" on a forum like this. When you start charging, you realize that only a fraction of people that would welcome these materials, will actually pay for them.
Just my two cents,
Dave
www.soundcloud.com/carovillano <---like all of us writing music, I would sincerely appreciate you taking a few moments to listen to a track or two and leaving feedback!