When you're far from the bubble (<1K Ly, I'd say), those sources are either some floating escape pods or data caches. There's not point in scooping them up since you can only discard them or sell them to black markets when back in a station (and not for much, on top of that). They just end up impeding your jump range.
Large data cache's are abotu 274,000 which seems pretty good to me (last time I sold one), escape pods aren't illegal salvage anymore (haven't been for a while) so you can sell them legally - work out for yourself whether you're selling the occupier into slavery in an imperial world or getting a reward for rescuing the pilot, but it's quite nice to rescue a few pilots from the black on your way home.
It seems reasonable that the threat indicator isn't 100% correct with what actually happens - clearly the pirates have been planning a cunning ambush, some "convoy dispersal patterns" threat 4 just have some T9s and a couple of small escort ships who don't bother you unless you attack them, presumably the size of the T9s throws it off.
Dropping in on them certainly adds some variety to the game, would be nice to get more things though I agree, hopefully some more variety and interconnectiveness will turn up at some point
