A lot of people are visually impaired and have a harder time using the app because they can't see the pictures. Alt text allowed for a description of what's on a picture (guy posing in the bathroom in front of the mirror showing off his abs after a shower)

Having the ability to add alt text to the picture you can allow more people to use it and find love/Lust.

You could combine it with text description that allows for context (like I'm the right)