There are two little things your advice glosses over:
1) Believe it or not, there are men out there for whom even that won't work. They might put up a half assed performance, but they may still act so disinterested so as to leave wifey feeling even lower than when she started. Oh yes, it's true, it's been known to happen, believe me.
2) Women don't just want to "**ck". Women want to make love and be made love to, which is of course ultimately consumated in the sex act. The emotional component is every bit as important to the woman as the visual stimulation is to the man. After a trist like the one you describe without any prior mental and emotional build-up, most women would feel no more than the exhilaration of being a hooker without the pay.
I've always said that's the problem with sharks - they're all bite and no lick.