They have more to gain by concentrating on the large churches...

They have more to gain by concentrating on the large churches which is still their stated strategy. Only once they have pulled in a high level of these, would there be an incentive to branch out wider with the much lower ARPC and higher overheads. I think the product is already largely self service but the company has a sales force to reach the large churches.
Look at the map of the USA and where their customers are based. There is still a lot of opportunity in states with just a low uptake.
There may be better opportunity in aligning the product with a wider range of charities (their new campaign function should be directly applicable) rather than chasing small customers.