I agree, but I wouldn't blame Purcell for that. I would blame Einstein himself, or more precisely the usual practice of teaching introductory special relativity in the form Einstein himself introduced it in 1905. It was Minkowski, not Einstein, who later introduced the 4-dimensional view of relativity, and Einstein even didn't like it in the beginning. (Later he accepted it in the formulation of his general relativity.) My point is, given that special relativity is presented to students in a non-covariant non-4-dimensional form, the ugly Purcell pedagogy of electrodynamics looks "more natural" than the elegant covariant formulation.