Originally Posted by
Anonymouswizard
TIEs are cheap and easy to produce, and even then the Empire began experimenting with models with shields at the time of the OT (I believe Vader's TIE was essentially a next generation prototype that had them and maybe a hyperdrive). Considering that twenty years before ANH the only interstellar starfighter we see required a large external ring but X-wings have one as standard it's possible that it wasn't until the time of the OT that the tech became cheap enough.
Because a TIE is pretty much just an engine with guns and wings.