Revell kit?

From an engineering point of view. In the 70's it was cheaper to make raised lines than recessed.

That kit number is the F105G, it's a good kit, the reason for the raised panel lines is a re-release from the early '80s. Bob

Don't know which kit you're talking about but Revell (and other manufacturers) do re-release older stuff and that's way their catalogues are a mixture of brand new, well enginered, detailled kits and older to very old kits that are no so nice by today's standards...

There's also a lot of mold-swapping going on between manufacturers and therefore you can find Monogram, Matchbox, Esci,.. kits marketed under the 'Revell' brand. If your model shop does not allow you to peek into the box, ask here first (and change model shop!)