Rather than why might the general populous, but who of YOU carry multiple bodies? Intent has become truth for me, and I'm finding myself use an E-P5 for my primes (bar the O60 macro) and an E-M1 for my zooms (plus the O60 macro). I'm not sure if ergonomics is the word I'd use...just feels right to in my hands. I've been known to head out and about with two bodies and four lenses. No one else? That, or did you buy two of the same body to avoid changes lenses?