And despite not being "formally" a part of the game, the fuel rats have become ingrained in Elite's lore and playerbase. It's known, pervasively, that the fuel rats exist, and that if you put out a distress signal, they _will_ come help you, come what may.
Occasionally, griefers put out false flags and attack the fuel rats that come to them. With no explicit coordination, this immediately became the most reviled form of piracy, in a game where piracy is broadly considered okay.
If you attack a fuel rat on the job, you can expect vigilante players to make you pay for it. You'll get bounties taken out, much better skilled and equipped players will hound you and blow you out of the sky, and generally pay back the fuel rats' losses tenfold.
You don't fuck with the fuel rats, either by choice, or because the entire galaxy has their back and will run you out of town if you mess about with the emergency service.