Apart from STIs which have already been mentioned and thread worms 
you can also very easily catch Giardia. a nasty parasite that lives in your intestines which pass through the bowel and out of the anal passage and can live for weeks outside the body and they will pass it on to you via rimming.
You end up having the worse case of sickness and diarrhea and cramps you have ever had and its a bastard to clear up as well. I caught this from rimming (no longer offer it) and I was ill for over three months even with treatment. You also then have the fun of telling everyone in your house they have to be treated as well as it can be passed on by touching objects in the bathroom like the taps etc
That is horrific catching something like that and not only being ill for ages but then you could have passed it on to your own family members and god knows how that conversation went and other punters so a big vicious circle and not worth putting yourself through that.
I have come across other escorts that have said they would never offer this due to other escorts they have known that have caught worms and your right it is easy to pass it on to family members you live with if your sharing towels, bathrooms etc.
I understand some men love this but have never understood why escorts would put this on there likes list and have to lick out loads of random mens bums, I can see maybe 2 people in a relationship might want to try it but to do it to everyone that comes through the door a bit of a turn off....
I think a lot of escorts feel pressured to offer as much as possible because so many escorts push the boundaries and so many punters expect a lot now days then from years ago but I think escorts should stick to there morals and don't do things that there uncomfortable with or a risk to there health.
As you have learnt the hard way by offering rimming do you now explain to any punters that ask you for it why you wont do it or do you say I just don't do that?
