I could be wrong but corners are just close enough (4-5 yards) that they can come up and make the tackle as soon as they catch it. Unless your qb can really fire it out there quick he is 1 on 1 with a Corner within a yard or 2 of the line of scrimmage. From my experience at the youth level if you coach the corner to react quick to that throw to just make the tackle and not go for the ball the WR can get smacked pretty good.
If you have a really big fast Receiver out there that can threaten deep you might get the corner backing up I just do not see many youth teams that can spare a really good player standing out there all the time. i have seen a couple teams get some yards outside vs this D by running off the corner and sending another guy into the flat (TE FB etc) if you get the LB stepping the wrong way with flow.
14th year youth coach 7-12 yr olds