Unless i know the person well im sure "hey let me hoover up mats while you kill everything and i don't contribute nothing to the wing" sounds about as appetizing as bacon cooked on a radiator, or at least that's a similar more political response to what i just got on Discord to test your theory and back up my own experience.
and typically we hang around in communities with similar interests, so yes majority of my friends list are dotted about the galaxy with no interest in combat other than when they're after mats themselves at which point we dont need to be fighting over PI's and its more efficient to do it solo. if drops were doubled in a wing it might encourage co-op play but until then... (and even then two ships harvesting with limpets will get very messy indeed!)
so its not that players overlook co-op its that it offers no benefit, even in the scenario you highlighted its all one sided, if it offered benefits for both players then people would be more inclined to let you tag along. (for example 'reward = Bounty X players in instance'.. who knows, or combat EXP = NPC Rank X player number multiplier) therefore the other player can earn more money or more exp for letting you tag along, (and those are just examples of rewards)
A good example was EXP leaching in Diablo 2 (IIRC), it was acceptable because more players = more loot & more EXP so there is incentive there to add them to a party both players gained something, but the minute the 'noob' started steeling unique loot then a new party quickly formed. its just human nature.
point is while there is no incentive to let you sit there hoovering mats up while not contributing, therefore co-op relies on an existing relationship or rare in game opportunity which isn't common practice, and probably why co-op doenst happen between strangers, but you're correct in the fact the dev's have overlooked the co-op potential here.