I don't necessarily think it's that... it's just a matter of a rush to respond/send quickly and not take a lot of time. It's pretty easy to either fat-finger when typing on a keyboard, or gesture input on a phone to get the wrong word and you hit send before realizing.

Sometimes I'll notice right after, delete and re-reply (social media) other times I'll just let it be... It's pedantic busy bodies that will single you out for a typo as opposed to discussing the idea at hand.