In the past, you would have to wander up to the person you liked and blurt out some embarrassing sentence that they would laugh at, and then it would take time and patience before something would come to be. Now, with online dating and Tinder, you skip all of the steps of finding and actively pursuing each other.
There's an extra layer of shame to being told you're an old slut. A young woman's "sluttiness" can be excused in part because she hasn't lived long enough to buy into social mores, and she's too hormonal to delay gratification. But an older woman who admits that she likes erotic pleasure without all the packaging? That's not just slutty, apparently, it's freakish.