Typewriters were/are monospaced, so putting a double space after the full-stop helped you recognise the start of a new sentence, giving it, and you, breathing space.
The PC fonts are size adjusted and double space is no longer necessary, but it doesn't hurt.
The ability to copy the URL of a video so I can paste it to NewPipe - or a setting where I can choose to use YouTube or NewPipe all red the time.