I turned it down all the time when my husband offered to, but for different reasons. It can be fun, but it almost never gets me off. Parnters in the past, including my husband, have let me know they felt like they failed if they couldn’t give me an orgasm that way. Even reassuring them it had nothing to do with them, and everything to do with the fact I rarely achieve an orgasm that way (trust me, they were doing nothing wrong), wasn’t enough. I enjoy it as part of foreplay, but when I feel pressured to achieve an orgasm, I’d much rather not even bother.