You can be dating one, but she's talking to (and possibly fucking) any of a dozen other guys and the desire to put in *any* effort to a woman like this falls to zero. It's a joke.
Women when they hear about this, would say some bullshit like "oh well that's why you say at the start of the talking stage to be exclusive", as if that awkward, weird fucking conversation topic would even go over well at all. Seriously, imagine saying something that stupid on a first date.
It used to just be assumed but now I don't want to play "ultimate gf manager 2000" and live my own life at the same time. Not only that but you know there was some guy that put in zero effort and got it for nothing, further disincentivizing any effort.

This leads to having to behave like a psychopathic narcissist if you want to get laid and unless you actually are one, it's a fucking chore and when you've had sex a few times it's actually just depressing because you feel like you are using the woman to masturbate with. There's no deeper connection and you realize when you start to think you might feel one, "oh yeah, she's talking to other guys, so this isn't special, and why the fuck should I go to so much effort for this?"