Girls use dating sites because similar to guys it's unfortunately the best place to meet new people once you're out of school/college. Think about it... I work a 9-5, have AP, have a house and a dog, what time do I have to go out and meet someone 'at a bar' or at the grocery store? First, I don't want to meet my future wife at a bar, not that I would be against meeting someone at a bar anyways, but I don't have high hopes in my 30's for meeting a quality girl to marry at a bar. Not saying it's impossible, just improbable. Next, most women have definitely adapted the "F YOU" tattoo on their forehead in public. I'm an in shape younger guy, but I swear if I even look at a girl in public she's instantly afraid I'm stalking her or going to rape her. Guys just can't talk to girls in public anymore (for the most part) due to women being terrified of every single guy. So online women feel safe because they can talk to you without you being physically present. Also, you get pictures, a bio, etc so you can learn a bit more about the person before ever meeting them (being physically vulnerable).
Not only that, but online dating is SKEWED very very much for women. Any kind of decent looking female will get a dozen new messages per day and essentially have her pick of the litter. Thus, online dating is PERFECT for the "perfect" girl because she can pick and choose exactly who she wants to meet with exactly whatever amount of interaction/chatting before meeting she desires.
All that being said, I think online dating is pretty much a joke... This pick of the litter stuff commonly leads to the "next shiny object" syndrome where women just drop conversations all the time and move on to the next shiny object they get a message from the next day.
I ran an experiment with online dating when I was using it a lot (hey, I'm a scientist...). I sent 100 "qualified" messages to 100 girls I was at least moderately attracted to, and didn't worry about other stuff in their profile that would be disqualifies even. A qualified message is at least 2-3 sentences long, giving a compliment, and highlighting commonalities or interest we share, then asking a question to encourage conversation. Of those 100 messages:
- 38 responses
- 17 lasted past 1 or 2 messages
- 9 lasted past a couple days of messaging
- 3 led to exchanging phone numbers
- I went on 2 disappointing dates.
This took months and constant effort to check online and message people back promptly before they got shiny object syndrome. I've also got to figure I've got a 1 up on your average guy... Good job, house, car, athletic, and have a bunch of hobbies. None the less, failure... Thus, it's also why guys online usually just try to hookup. There's a HIGHER SUCCESS RATE for putting in ZERO EFFORT other than "hey wanna hook up?"
After that I disappointment, I of course had to run the experiment the other way... I sent out around 50 "hey, wanna hook up?" messages and got a 75% return message rate (as opposed to HALF that sending a 'qualified' message). Half of those responses were "no, blah blah blah" but even of those "no's" it led to conversations that led to potential meetings! After this experiment it's baffling to me that people still "try" with online dating. It's a joke and is goin to fail once ever guy realizes they'll have better odds saying "wanna hook up?" and women will not get the pedestal treatment they get put on anymore online since all guys just wanna hook up (as a result of their previous shiny object syndrome).