Why should you bother making your site accessible? Because more people need it than you might at first think.
Even if you discount the 3-in-4 people who wear glasses or contact lenses, at least 1-in-5 people have a disability.
That's 21% of your audience. Why would you shut out 21% of your audience?
Then there are people with 'temporary' disabilities - poor lighting/environment, using their phone/computer with one hand because of injury, and so on.
Finally, good accessibility makes things more usable for everyone.
Estimate how many people using your website might be disabled