In many developed countries, the hacker events and board game nights are organized over Facebook groups; Facebook itself is dead, except for the events niche because people don't see a better place to announce these things; people aren't necessarily doing flyers posted on a message board like in the 1990s.

Also, in not all countries is it acceptable to talk to strangers in public, like your pizza place example. In Finland this will make people very uncomfortable, though you might get away with it if you are a obvious clueless foreigner (or an unusually charismatic foreigner). About the only place it is acceptable is bars after a certain level of inebriation, but that is not the kind of interaction many people will find worthwhile.

The Nordic countries have been like that for long years, but I think this taboo is spreading because young people in some Central and even Southern European cities, even with a history of cafe culture and large student populations, are complaining online about the difficulty of meeting anyone when out and about. Telling someone that they should just take the first step isn't necessarily a solution, because like climate change or recycling, this is maybe something that cannot be solved by idealistic individual action but requires policy changes.