You're thinking about the wrong stage of friendmaking.

The pitch here is for getting people over the first hurdle, which is being at the same place at the same time as other people, and to some extent, the second hurdle, which is striking up a conversation (as anyone who would attend something like this is, by their presence, signalling an interest in at least casual interaction with the other participants). This adds people to your "acquaintances" list.

The next step is forming setting specific friendships. Your gym buddies, your work friends, etc. Then you need to actually invite some of those friends to other settings, until your friendship isn't entirely predicated on the particular setting. Then you need to spend enough time with that person to maintain the friendship.

For most people, the big hurdles are the "being present", "striking up a conversation", and "converting setting specific friendships into general friendships" steps. Everything else is pretty straightforward.

Casually dropping by someone's place unscheduled is typically reserved for pretty close friends. That's not what this service is targeting.