Imagine a future (say 30 years from now) where your societal problem is being addressed at scale. Is the problem completely eradicated? Or will there continue to be a need for solutions like yours?
There are two reasons why the problem might not exist anymore:
The first is mission achievement. The problem has been eradicated and there’s no need for your solution any more. An example of this might be the Smallpox eradication campaign in the 20th century. Most problems can’t be completely eradicated – so be critical when considering whether this is possible.
The second reason is the problem still exists but is being addressed by alternative and more sustainable means. For example a change in government policy that tackles a particular issue at a systemic level, e.g. achieving benefits reforms rather than running a food bank.
If your problem can be solved in the future, you might not need a doer and a payer to sustain your impact.
However, if you need the solution to be delivered continuously, the questions of the doer and payer are critical for sustainable impact at scale.