There are pack of trader and his security, and while trader is Clean and part of security too, some security could be Offenders. They still do not attack, as they are paid to protect the trader.But if you attack anyone of them (even the Offender), they all go after you and still are Clean (and you are Clean, if you defend them too, after they start firing on you).
Parcels/passengers/cargo runs are mainly for better equiped ships, and it provides something to do, when just hoarding equipement does not work anymore.
Still some may be done on low level and slowly build your rep, with some small pocket money (I - on the begining - take just what goes around the way I plan to travel anyway - so it is like 1 in 20 stations or less, but still it counts. The game remember up to 70 of each and you are total top, when all are delivered. till there is small variance, in some systems they "do not know it all", but in save file the values are intact).
After Cobra mk III phase I usually go for Boa 2 cruiser and delivering 1.000's of gold/gemstones/... really pay nice bounties in even one run - and you can load/offload all of that on one place, not restricted by usual 127/255 items limit.
Still it is not way to be rich, it is way to not be bored, once you are rich

(As well as RSS missions and many others)
(Yes, some of us, as myself, spend insane time in one pilot - I want to travel all planets of all galaxies (now nearly finished first two), get max on each ranking (RSS, 3 couriers, state packages (and later with better reputation also pirates elimination), etc, etc - no matter, that my current ship could not be improved more and I have Elite status long time ... ) - it is not game to win, it is place to live

Lady of Fate, we adore you . . .