When you use images with text in them--like screenshots or strings of text, people who use screen readers cannot interpret them. A screen reader is software installed on a computer that allows visually impaired people to read text on the screen.
It gathers information about the page and provides output to the visually impaired user with synthesized speech. People who use screen readers navigate their computer using keyboard commands.
With that out of the way, why should you care?
Because screen readers cannot interpret images!
This means your screenshots, images of sales pages on WSOs, software that is not compliant with accesssibility guidelines, optin form images with text in them, webpage images . . . ALL BECOME USELESS!
There are ways around this, and if you start applying them, you won't lose so many customers.
--Make your software accesssible with keyboard shorcuts and correct labeling. Test it with a screen reader before it goes live.
--For screenshots, optin forms, and webpages: use the alt text properly! Put a useful description in this field, whether it's the amount of the screenshot, text of the optin form, a helpful "Fountain pen logo" . . . Keyword-stuffing doesn't help the user!
--You could also make your optin form images text.
--Make your WSO images text or at least offer an alternate accessible page.
I know this sounds like a lot of work, but with repetition, it will become second nature. I for one am sick of requesting refunds because I can't use a piece of software. If you ignore the issue, you lose a customer, but help them out and you've got one for life!