Drive traffic to your website when people search keywords in Google Image Search. Uploading a photograph called IMG_6408 is not going to work very well. Either is renaming it by date for internal archival purposes. An algorithm can’t see what is in a photograph so we have to rename photographs so that they are optimised for search engines.
I have seen a number of business owners who don’t have time for social media and assign it to an inexperienced employee or a family member offers to handle it for them. I will leave the argument “is this a good idea” aside for the moment. Please remember this person is shaping your online identity, their posts/tweets are a representation of your business.