Structural engineering, or any other kind of real engineering (which includes every time of engineering except software "engineering") can also be reduced down to pure math. It's complicated math, and not everybody can comprehend it, but what engineers do boils down to lots and lots of equations. The only place this really applied in software is in efficiency calculations: is approach _x_ faster than approach _y_? In general this is considered a waste of time by most of the "stakeholders" (that is, the people who are signing the paychecks), at least until it's too late.
Software engineering can be reduced to math too, for example functional programming is a lambda calculus derivative. I think it's basically just that we're so close to programming that it's hard to see it for what it is, just a bunch of rules and equations.
That's just one facet of software engineering. Large swaths of it cannot be reduced to math ie everything the user actually sees, hears, perceives, etc. Those are subject to psychology, aesthetics, ergonomics ... Although we're trying to quantify those, too, so maybe one day ...
