Fame
You may not be known by name, but your work may be. However, if you engineer a spacecraft that actually sees some space time, or design the fastest military aircraft, or the most accurate or deadly missile, who knows—you could get your face on the cover of Time.(That's a magazine. Yes, like Glamour and Teen Beat.)
On the other side of the coin, you don't want to be famous for a flop, or a craft that claims any lives. (Unless it's in the course of battle, and you're at peace with that sort of thing.) Now that you think about it, engineering away in obscurity suits you just fine.