My personal take on this:
Q: why do they use a screenshot with a typo.
A: Maybe to bring attention to the font? To the letters that are missing or those that are present? Maybe just because they can.
Q: Why are all these companies designing their own fonts. It's not needed...
A: Many reasons. It can be cheaper than licensing other fonts. It makes their apps (and brand) stand out. Or people might find it more aesthetically pleasing. The perceived `need` for it, has nothing to do with whether or not you need it for their app/website to function properly. And maybe `jarring` is exactly what they want.