I agree and I'll add, the excitement of imagining what she is doing without you can be amazing. Plus, trusting them to fuck without you can lead to amazing fun between the three of you together
I love it when she tells me she did something she said she would not, or that I had said I didn't want her to do. I love the feeling that I cannot control her, and that I never know what she might do. She says she does not want anal, has never done it and never would. But then she was with this guy who wanted it from her very badly, and she started to research it, how to do it, how to prepare, etc. She asked me if she "should". I asked her if she wanted to and she said she didn't, but I could tell from her answer that she wanted to please him and to try it with him. She got lube for it and was planning that she would, but their connection fell apart and they never did.
I know she's not just making up her resistance to it, because sometimes when in the heat of activity, my cock inadvertently gets misaligned and heads in that direction she panics and pulls away, with a hint of anger at me over it even. Her desire to please a lover and to make him think of her as super hot in the bed will lead her to do it with someone in the future at some point if he is a regular who keeps wanting it. Whether she will tell me, I cannot be sure, but in my experience, she ends up telling me everything at some point, even when she may realize she probably shouldn't. more likely, she'd ask me again if she "should".
On one hand, I don't want her to. Especially if she won't also do it with me (she won't). Like with giving head. She's done it for me, especially early on, but she doesn't really like to do it. Not for a lover either, but for a lover, her eagerness to please and to be perceived as a hot lover allows her to overcome that and to indulge completely. The thought of her giving her virgin ass to someone else turns me on tremendously...and fills me with angst!