Философский вопрос, а заем вообще нужен атрибут disabled?
Зачем нужен readonly, когда есть disabled..?
А вообще, вот (в зеленой плашке):The difference between disabled and readonly is that read-only controls are still focusable, so the user can still select the text and interact with it, whereas disabled controls are entirely non-interactive. (For this reason, only text controls can be made read-only: it wouldn't make sense for checkboxes or buttons, for instances.)
Для вывода какого-то промежуточного результата