Wearing a respirator is important to me for multiple reasons. In general, I approach it as a basic hygiene measure, like washing my hands or using hot water to clean my dishes. This was further solidified when I learned that masking is better at keeping your germs to yourself than preventing new germ uptake.
A lot of pathogens – like covid, measles, and tuberculosis – are airborne. This means they can travel in tiny respiratory droplets we release as we breathe, speak, sing, and shout. They can also linger in the air for quite awhile (measles lasting about 2 hours after an infected person has left the room).
Additionally, we can still be contagious even if we aren't experiencing any symptoms. Maybe our illness is in the pre-symptomatic stage. Maybe our symptoms are just so mild, we don't even notice, or mistake them for something else. (I know when my allergies are at their worst, it feels like a flu.)
Another thing – more people are medically vulnerable than one might think. Unless they tell you, you don't know who's immunocompromised, has sleep apnea, or is dealing with heart issues. Covid itself can cause these issues, since it's a virus that targets multiple organ systems. Some people may even have these issues already, but don't know it!
It was always weird to me how the US "wrapped up" the COVID-19 pandemic. The CDC advised using respirators like N95s and N99s as opposed to medical masks (aka "baggy blues"), then about two weeks later, eased guidelines and then, a few months after that, Biden basically said, "okay we're done! :)" When Biden said that, COVID was still roaring across the US. The virus didn't suddenly disappear between 1 to 7 months. There was only a month in which the CDC promoted the tighter mask recommendations, and even then, most people were still wearing loose medical masks or layered fabric masks! (And we're not even getting into how the CDC lied at the start of taking the pandemic seriously, saying that masks weren't effective.)