I think everyone would probably want to do it the old fashioned way, either be introduced or meet through work, school, whatever.
However once you reach a certain age, it really does become harder than you expect to meet potential mates. Once you're out of college, settled in a job, have a smaller group of friends, you don't meet as many new people as when you were younger. So that's where the higher numbers come from.
Plus it might also be easier to do it online. You get to see similar interests, goals, talk in a non-threatening environment, it makes sense in a lot of ways. For the most part you still do most of the actual "work" in person... there's only so much you can get to know a person via the internet. So you talk online for a bit, see if you think you're compatible, then meet in person and try from there. When people hear online dating they often assume you have dates via webcam and chat online 4 hours a night, that usually isn't how it works.
It also makes sense for middle-aged people, those who have gone through divorce or are widowed... it's even harder to meet single people your age 40+, so I think it's a great benefit to have available.
