From Google:

> Partiful does not make money yet. They are a venture-backed startup with many millions of dollars of funding. They will eventually offer a premium version, an ad-supported model, or be acquired by a larger company like Eventbrite, Ticketmaster, Snapchat, or one of these other potential acquirers.

Basically, enjoy it while you can. There is nothing wrong with using a free service like this while you can. Best case IMO is that they monetize it with low fees and have a product that is actually worth paying for.