Alt text helps everyone.
I have a difficult time understanding some memes. Often, I click on the alt text for more context.
Most of the time the extra info enlightens me, I suddenly understand the meme, and move on. Thank you for the alt text.
Case in point. Today I saw a meme photograph from the point of view of someone writing code on a laptop. Lovely scenery can be seen through a window. The caption "I love coding on the train" seemed banal.
Because the post had indications it was a meme, I dug further and clicked on the alt text, which explained that the idiot that took the photo and posted it publicly was revealing some very private bits of code visible on the screen.
Had there been no alt text, I would have missed this entirely. I'm not blind or visually impaired, but alt text helps me on the regular.