It's funny cause i live in a very sexually active community, with bdsm, porn pro, ex prostitute, etc. The people being recognize as the sexiest and having the most partners never, ever ask anything.
I have the very unique life style that makes half of my friends also hard core geeks, d&d players, hairy sysadmin, or able to tell which multiverse this particular batman costume is. They are also doubting every of their moves : is it allowed, it it disrespectful, will the other one be offended or hurt ? They really don't have much sexual success.
I love both of my groups, and none in them exhibit any signs they are better or worse persons. But i didn't experience that explicitly asking for consent made things better.
Not being an asshole does, and is pretty much unrelated to sex.
But such services won't work as consent can be revoked anytime. It doesn't matter if you signed a contract, you can at any point say "No" and the consent is gone.