Can't say why girls do that to some guys, but I can tell you I do the same to girls. Figure I'd just offer my perspective.

Ultimately it all comes down to how a girl comes off. Some girls come off/talk to you like they want to date you, while other girls, come off/talk to you like they just wanna have fun. And so, just realistically speaking, if you come of as you wanna date, then I'm gonna try to make sure that you actually are here to date, and that you fit what I look for in a long term relationship partner, as well as not have hidden motives. That vetting process takes time, and I'm trying to see if we are able to develop a friendship, really get to know each other, can work with each other's personalities and have good communication.

While guys may have the agenda of 'sex' a lot, girls that act like they want to date also have plenty of agendas. I'd say, some common agendas are, someone to solve their loneliness, someone to boost their self esteem, someone they can introduce to their parents to get them off their backs, someone to provide them with their emotional needs cuz they are just insecure and needy, or just someone with money, etc... I'm sure guys do the same as well, except 'sex' just seems to be the most prominent ulterior motive with guys, while with girls, it could vary a lot.

But no matter what, taking the time, means I see you as someone dateable, so I'm not trying to rush into things, and I want to see if the this can stand the test of time. There are A LOT of drama, impulsive, girls running around out there and in a LTR, gotta make sure I get into something that can last.

So, I as a guy, do a lot of the same things as girls. I take my time with the dateable girl, text her only when I actually do think of her and want to talk to her, ask her out when I actually do want to go out, same with calling her, although I will 1000% be more thoughtful in my interactions with her. I wouldn't try to pressure her or come on super strong - it's more about ebbs and flows. And then the girls that give of fun vibes, I'd probably pressure / ask them to come over on the first date, cuz I'm a dude and I like sex. I'd ask them out, pretty quickly just to close the deal, and then I probably slowly fade unless she was super fun.