I was kind of wondering the same thing, I even docked at a station I have 6 Allied factions with and I'm pretty sure the mat rewards are just Goods and Data, which is fine by me because I would rather use missions for stuff you can't trade for.
I would like to reiterate that while "Tech" might not be as "Rare" as Circuits or Chemicals, you seem to need a lot more "Value" out of the tech items. 90% of the Tech items I am finding are Chips that are worth like 2 trading points and you need 18 for a single Weapon Component, which is needed for all Kinetic Weapon upgrades. In Contrast, Graphene which is the most valuable Chemical, is found like everywhere.
Also on the subject of only picking up certain assets and leaving others, it sounds like a decent idea on paper, but when I'm fast pace looting settlements over and over, I would rather just gather everything so I don't need to think about what to pickup or not, fill up my Storage, then go trade at a bartender to free up space. This is also good for having other Assets available for buying Mods.