I've benefited from lots of theoretical classes, and you're absolutely right that you need to understand the theory of what you're doing. For example, I took a

I've benefited from lots of theoretical classes, and you're absolutely right that you need to understand the theory of what you're doing. For example, I took a lovely class from Prof. John Hooker (at CMU) that derived Linear Programming duality as a natural consequence of Farkas' Lemma, rather than just mechanically grinding through LP tableau. I certainly followed the proofs discussed in many classes. However, I can honestly say I got that understanding without doing hardly any proofs of my own. Graph theory was the only class where I "did proofs", and I didn't find it my favorite. (Later I did algorithmic graph theory and network flows - and that was fantastic, with no proofs.) I guess my point is just that an engineer can understand and use a lot of pretty advanced math without spending much effort learning about proof techniques. That certainly wouldn't be how I'd spend my time. (Of course, if you enjoy doing that then knock yourself out.)