One thing i've found is that it may not be that your W's may not want to be seduced, but they may not be want to be seduced by you, or may be totally turned off by your approach at seduction.
Many a spouse on this board has been completely frigid for years and years only to go completely wild with the right stranger.
Consider this "why" should she have sex with you? What do you bring to the table to make it worth the effort.
Or...
Would a woman who is not your wife be easily seduced by you?
Sexy is sexy whether married or not, so would your wife think of you as sexy?
Saying she doesn't think anyone is sexy is not a valid answer either since many a spouse has heard this and found themselves cheated on.