If you design your website simply, you don't need to know that the user is using a screen-reader, nor what other strange situation that you'd never even imagine

If you design your website simply, you don't need to know that the user is using a screen-reader, nor what other strange situation that you'd never even imagined or accounted for may be happening. They'll be able to use it either way, because you made it universally accessible, rather than covering certain classes or cases individually.