Well, DSLR/MILCs really aren't that different from film SLRs. The sensor replaced the film to be exposed, and the battery replaced the film cannister. For mirro

Well, DSLR/MILCs really aren't that different from film SLRs. The sensor replaced the film to be exposed, and the battery replaced the film cannister. For mirrorless cameras the EVF replaced the reflex mechanism. Everything else is the same, so with similar design constraints it makes sense a similar form factor would emerge.