I've spent a lot of time with women in my life (sexually, platonically, family), and most can agree with this statement. Almost all of them are bored out of their minds. Most girls go to work/class go home, lounge and watch netflix, eat some food that's awful for them. They then proceed to stay up late watching some crappy movie then wake up miserable to repeat the process. For some you can throw in an extra activity like going to the gym or cooking. Most aren't doing that so I'd say my breakdown is fairly accurate for a large portion of women (and sadly men too).
As a highlighted before, most girls days are insanely mundane. Forget those pics you see on social media too of them having "fun" on the weekend. Have you ever gone out with groups of girls? It's fun, but most of the time they're just buying cute drinks or a beer if they want to look cool, and then taking multiple selfies and group pics to make it look like their having a fucking blast. Most of the times girls go out and dress up in groups like this is mainly for attention. A small proportion are actually looking or are open to a casual penis in the mouth or booty, but most are not down for anything, but validation.
If you ever talk to a girl in the middle of the week i.e. flirt, even if she's not interested she'll be pretty flattered. If you're an attractive (lean, well groomed, well dressed) guy or at least look cool, most girls will be excited that you'd even compliment them or say anything nice.
On the other spectrum, even if you're not great looking and the girl is kind of rude or mean, she's still pretty excited. Now she can go home and humble brag and complain about how some creep said she was sexy or hit on her. She'll be happy with the self esteem boost even if she rejects you.
Even most sexy girls are not getting hit on often in the middle of the day. Most guys will stare or creep and say nothing. I've seen it happen all the time. Most guys only approach with a steady helping of liquid courage, and doing it then has no real impact and means nothing. Getting hit on by you in the middle of the week/day is the most flattering thing and exciting thing that happened all week.
Even I get excited when a girl compliments me and says something really nice to me. It sticks in my head and can really make my day or week. It could come from an old Hispanic lady at Shoprite telling me how tall and handsome I am or from a girl at a bar. I still get pretty happy when I remember a girl calling me muscular a week or two ago.
Most people are bored. Hitting on them or flirting with them is the most exciting thing they'll do. Even if you strike out they'll still be excited and happy about it in some way. Quit being selfish and go make someone's week.
TLDR; most girls want some attention. It makes them feel cute/validated/sexy when someone hits on them or gives them a nice compliment. Worst case scenario she rejects you or calls you a creep