Cream-pie eating is a two-sided fetish.
My introduction was with an affair partner who was also a cheater - on a fairly regular basis, she would have me lick and suck her pussy after we had sex, and clean up my own cum. Later, it became part of her dominant behavior to come home freshly-fucked from one of her adulterous encounters, usually after a "girls night out," then have me go down on her, thinking I wasn't aware, either of her cheating, or the fact that her pussy was full of cum. I knew each and every time, and toward the end of our relationship I recalled for her every time it happened.
My wife loves oral sex - I usually prepare her by giving her two to three orgasms, because it makes it easier for her to take my cock. We make love, then I finish her again orally, and enjoy my own cream-pie. With respect to other sources of cream, since I am a participant in 50% or more of her encounters, and oral sex is a big part of those encounters, there is lots of pie-eating on both my part, and her lover's part. When KK does a solo encounter, the outcome is varied - sometimes I do clean her up orally, sometimes she enjoys my hard cock in her cream-filled pussy, other times, she masturbates and teases with her lover's cum while telling me about the encounter.