And even if we would accept that some stay behind a lot in the crafting tier, the parts for weapons/armor/tools are a problem, those seem to be tied to the skill aswell in loot. We have tons of parts for the skills of the people who go looting. And not a single pistol part or steel tool part and one steel armor part on day 21 wich are 3 of the crafting skills the stay at home people have. Plenty of parts for the skills that the players that go looting have. More than we ever need, like 20 steel spear parts for example.
I've put about 40 hours into A21 now, one spear build for 313, and I started over with an Int build for 317, both with maxed out Miner 69'er, and I've found a total of 4 steel tool parts. I had about 40 steel spear parts in the spear playthrough, and have 60-70 combined robotics/baton parts in my Int playthrough.
Pretty sure I've found more motor tool parts than steel tool parts. Either I'm cursed, or steel tool parts are exceedingly rare.
Also, the specialization thing really seems to screw with loot drops. I'm on Day 9 of my Int playthrough (I play 2 hour days) and I just found a q2 wrench. I've had a q1 wrench, and I can craft a q2 (but didn't see the point.) Found probably half a dozen q1/q2 stun batons (all after I'd already made a q5). Found a q6 Iron Pickaxe in the snow on like Day 3, a q6 Iron Fireaxe in the Desert on Day 8, and everything else is still q3 or lower pipe garbage.
It really seems like one will have to specialize in everything to eventually get decent drops for Salvage Tools, Turrets, etc. that aren't directly a part of their desired kit.
Edit: I just checked and I have 52 robotics parts and 39 baton parts (after making a q5 stun baton) in my Int playthrough. 2 steel tool parts, and you need 20 to make a full set of tools (5 each for Pick/Axe/Shovel, 5 for Ratchet.) I won't ever need to make another baton, and given that a q5 turret costs 50 duct tape, I doubt I'll ever make more than 2 of those.