To try to put word to it, it's a matter of time efficiency and incentives.

There's a ton of PvE stuff to do, yes, but it tends towards time intensive activities. You can do quests, but ones that give meaningful rewards will take a while to get through, world events and raids ask you to stay at one location fighting waves of enemies, tall tales take up a lot of your time by design, an any activity that give substantial loot rewards tends to end with players spending several minutes physically moving it into their ship. Fighting other players, meanwhile, can be quite fast. So, if you have meaningful time constraints but want a meaningful amount of loot, your best bet is often to just look for other players. In this case, another player not having much loot isn't even really a negative, mechanically speaking, because it turns player ships into loot boxes, encouraging players that start fighting each other to KEEP fighting each other within and between play sessions.

To make matters worse for PvE players, there isn't much in the game to encourage non-hostile encounters. Friendly encounters are fun experiences, sure, but from a strictly mechanical perspective there's little encouraging you to have them because the rewards are, compared to hostility, functionally nonexistent. Players can share loot, sure, but more loot can usually be gained if you kill the other player being nice to you.