It has already been said pretty well but I do want to say this. I also disagree with the fact that with time you can "skip steps" because you are more experienced. As a health care provider you should never skip steps, I think it may seem that way when you look at the seasoned paramedics because they are able to use the experience they have to go straight into the assessment and treatments required for that problem (searching for that differential diagnosis).
As a brand new EMT you don't have that experience to fall back on, so you do the entire body assessment no matter the problem.With time you learn what it is you are looking for, what you can do later into your assessment, you learn what the priority is for most circumstances. Nothing is ever bypassed, you are just more efficient at what you do.