Instant background checks are only required when going through an FFL, not for private sales. This was the compromise that was worked out in order to get background checks for gun stores. Trying to regulate private sales was a sure political loser back then and it still is. Most all gun control measures are big losers for libs despite the media playing it up every time there is a shooting.
Requiring checks for all gun sales makes creating a list of gun owners much easier. Libs want that list eventually so confiscation can occur. It's obvious, but there are too many gun owners in this country for that to ever be politically viable.