Furthermore, a lot of nonprofits are financing at least part of their operations through grants. Those grants often require them to prove that they work was completed and done so in compliance with the grant terms. Photographs could be part of the evidence they collect to document how they used the funds.
Interesting that even in the chain of events depicted in the comments it's started and ended by Republicans and the poster assigns all the blame to Democrats.
This is why it's common in the black community to get a receipt whenever you buy anything. You can't prove where you are at all times, but you can prove that you were at a particular time and place. Might save you from being railroaded for a crime you didn't commit.
Furthermore, a lot of nonprofits are financing at least part of their operations through grants. Those grants often require them to prove that they work was completed and done so in compliance with the grant terms. Photographs could be part of the evidence they collect to document how they used the funds.