some of the ids such as the LWB and afa ids allow them to attack on sight any ship carrying syth paste allied pilots and etc and i think the admins made the selling locations on some commendibles in houses where such pirates that can attack on sight ships that are carrying such items. im not completely sure on the selling location part.
Also for some items such as gate lane parts carrying them when not having agenia ID can have in-character consequences. So in order to transport some items they need a specific id such as that or they could get into trouble with lawful forces or the company that makes them. Also lane hackers can attack you on sight because of this so using a foriegn id cant protect you when you carry certain items.
Theres more examples then just this one this is the only one i can remember off hand
Ive had enough of disco for now. I might be back at the next mod release.
The Master of all things cyborg