Yes, this is one of the things people take different positions on and the most important thing is that you're comfortable with your choice, whatever it is.
There's a demand for it and a demand for people who don't do it (but not so much in the male market!)
I hadn't heard the "I don't want to be partly responsible for someone's wife getting the clap" reason much before (although I know of someone who puts off clients in relationships from seeing them) because, yes, "it's the guys that should be covering themselves against that".
If they want to take the risk of getting an uncovered blowjob, they need to live with any consequences - no-one's tying them down and doing it to them, unless that's what they paid for