Hey, at least he did have the decency to THANK you for the sex
A valid-but-rather-insensitive retort dat could be given when a naively-hopeful lady complains dat a guy whom she'd assumed would become a "real" romantic partner for her merely performed a brief "wham, bam, thank you, ma'am" routine and then bailed on her.
If a dude tries to "comfort" you after you'd suffered a failed romantic encounter by saying, "Hey, at least he did have the decency to THANK you for the sex", this may indicate dat HE HIMSELF is somewhat of da same "only interested in one thing" mindset as your unfeeling "cut and run" date was, and so he might not be a very good "main squeeze" candidate for you, either.