Plenty of people do hobbies because they want to do hobbies, not to find someone to date. If you date someone from your hobby group then break up, it can fuck up your hobby group. Same risk if you ask someone out and it's poorly received. Depending on the hobby it's harder to find new people for that than it is to find someone else to date. It's similar to dating someone at work in a lot of ways.

The big benefit to online dating is that people are there because they want to date someone.