Why can't I take a Scrap Yard mission on top of a Combat mission?

Because the Developers at Guild Software are dedicated to the fight against ADD & ADHD.

Seriously, old topic that deserves a +1

Yep. +1

We used to do that actually. I got a char to 10/10/10 in a couple hours of pvp. It required you to gather 8 players for optimal strength, so we grabbed as many noobs as we could and brought them to the fight. Too bad that was considered an exploit.

I think they've been trying to keep it simple for debugging purposes.

I asked the same question a few years back. There are some missions that don't seem mutually exclusive.

Killing Spree/the one where you need to bring back Bot scrap.
Mining/prospecting
Escort/retrieval or any delivery mission where they only need to deliver a few CUs
etc...etc...etc...

answer: because code is complex, and maintainability is paramount.

nevertheless, +1.

This is without a doubt the most counter-intuitive hole in the game. Look at EVN, FFS.