Most people regardless of gender are very hesitant to boldly reveal and express how they truly feel deep down about someone they've been admiring. That's because most people get shy around someone they really like so they'll will beat around the bush. If ANYONE is attracted to anyone 90% the time it's initially going to manifest itself as subtle things like saying "Hi" to your crush everyday or being nice and it likely won't be anymore flagrant and obvious than that. It's just that a majority of men later follow up on this and ask their crush out eventually. While a minority of women follow up by confessing or asking a man out. Just like everyone else most girls are too shy or giddy to go up to their crush and ask them out.

Most women will shoot their shot by either being nice to you, smiling at you, looking at you for 2 seconds or thinking about you. Most women would rather do witchcraft and try to "manifest" you than outright telling you to your face that they are attracted to you and I'm not even joking. So if you're a guy who thinks a girl might be into you because she's merely being nice to you or because she said "Hi" to you it's very reasonable to think she's flirting with you because most women shoot their shot in subtle ways. It's not such a ridiculous thought.