Have you ever been confused about how some one would like to you just to get you in bed? Same here. Turns out that sciences has found we are more likely to lie when we are trying to get laid or when we are "sexually primed".
It turns out the ability to lie signifies a certain level of brain development. We don't condone lying to get laid, but now at least we can understand that it happens for a reason.
References
Why People Tell Lies about Sex