The standard calculus course does not acquaint the student with the reasons why calculus has been and continues to be important in the intellectual development of humankind. Rather, it attempts to prepare students for other courses in which they might learn that. (To revamp the standard calculus course to do that would be at the cost of scrapping maybe 90% of what's now in the standard course. Deal with it!)
A graduate-level algebra course like Nathan Jacobson's Basic Algebra I and II likewise only prepares students for other courses (maybe algebraic geometry, number theory, and some other things?) in which they learn the motivations.
Of what proportion of math courses in the conventional curriculum can it be said that the motivations are deferred until the student takes some other course?
Just answer that and ignore the next question, unless you don't ignore the next question: What are the pros and cons of changing that?
This is what we have instructors for... I always tried (I don't know how successfully) to give my students some idea of the motivations behind the course. In the case of calculus, for example, I talked about the dynamical theory of planetary motions and how this contributed to the mechanistic world-view.