Even if one has no intention of making a profit, the accounting still has to be done, the books still have to balance, and there has to be enough revenue to cover the expenses.
Sure, you have to account for things (especially if you are a registered not for profit), but as long as Donations >= Expenses you don't really have to worry all that much about a 'business model'.
In fact, it often happens in reverse for these sorts of clubs/societies - Because the base expenses are very low (a £11.99 zoom account and to start with it is volunteer-led) rather than requiring enough revenue to cover expenses, you usually gather donations which let you spend money, and you don't spend money that hasn't already been donated. If less money gets donated, you can just slow down spending.
In terms of not for profits here we aren't talking about a company the size of Oxfam - we are talking about a reading group that has 12 volunteer hosts.
Even if one has no intention of making a profit, the accounting still has to be done, the books still have to balance, and there has to be enough revenue to cover the expenses.