It works in hostels because like you said, most people are traveling. This means they're only in the city for a night or two, so they want to socialize, meet lo

It works in hostels because like you said, most people are traveling. This means they're only in the city for a night or two, so they want to socialize, meet local people or other travelers as part of their adventure, go out together, etc. This doesn't work the same in other 'social' places. If you visit a coffee shop, 90% of people are meeting friends, doing work, or want to drink alone and browse the internet. I don't know how you'd start a place that only encourages visitors that want to meet new friends. What about a coffee shop that only has big round tables with 10 seats, so you need to share tables with a handful of strangers and face each other? You could try local CouchSurfing meetups. I've been to some alone, and depending on the city they might have 5 or 100 people. They're typically at pubs, and some are better than others, but they're usually a mix of locals and travelers from around the world. Quite a few others go alone, so it's relatively easy to make some friends.