I don't think it is so much of a styling decision as a choice of efficiency. They already had the tooling for decades from the FM and FE lines. Very simple to not do any styling, and leave the development expenses to the electro-mechanical construction. I think that Nikon could not have expected many sales, so why put more money in styling. Even if they had made it look modern the reality is that it was introduced as a manual focus and manual film advance camera body in a world full of autofocus and motordrives.
Originally Posted by ajuk
Sure, it looks old school or retro, but I don't think that is a bad thing. When I compare an FM3A to the previous versions, I find the best and strongest feeling with the original FM and FE; then the FE2 and FM2 seem slightly less rugged . . . all these are durable cameras, but modernizing or cost cutting changed the feel. It would still take some abusive behavior to damage any version.
P.S. - Thanks to all for this discussion. I enjoy this series of cameras.