Temporary impairments are a massive thing to consider! One example I recall was that Facebook learned video engagement rose massively when subtitles were added

Temporary impairments are a massive thing to consider! One example I recall was that Facebook learned video engagement rose massively when subtitles were added because most people scrolling through Facebook on their phone don't have sound on due to the environment (work, commuting, etc.). Another example that I'm always complaining to designers about is that low contrast text might look fine when you are designing something on your desktop machine indoors, but take it outside on a phone and a sunny day might make it all unreadable.