What happens in a couple of years time when all your contracted fly halves are on the wrong side of 30 and every half decent option has been signed elsewhere?
Super Rugby sides are limited to roughly 40 contracted positions and within that they have to compete in the current season as well as plan for the future. If they don't sign talented young players, other sides will. They won't just sit in club rugby waiting until the Reds coming knocking if there are other options available.
The teams also want to be able to help control the development of the player and that is another reason for signing them when young.
Rotation is best in Super Rugby I believe, up to a point of course. If a player does not cut it he does not cut it, but for the most part players given equal opportunity and being under similar guidance will achieve similar levels of success.
It is only this season with the rotation policy implemented (unofficially) in SA that I have started to notice this. The Sharks won with a weakened team against the Kings - barely, but it will be experience in good stead down the line for them. Last year the Stormers drew against the Sunwolves, this year they sent a depleted and young team over there and won a hard fought battle (a lot of the Stormers' rotation is due to injuries of course).
Sort of mid-season another competition kicks off in SA - the SuperSport challenge, which includes 15 sides including 1 from Namibia, which offers those on the fringes of Super Rugby squads the opportunity to get game time should they be needed.
Robert du Preez for the stormers has 8 or 9 caps for the Stormers but is currently more experienced than his 12 and 13 and for now they are still winning the games they are expected to win.
This sort of mindset has been enforced also by the continuous outflow of players to Europe and Japan, I reckon SA suffers the greatest loss of players here.
Don't play Quade every week is my viewpoint for example. If you're playing a team you expect to beat, put a youngster in there. If you don't beat them your squad will have built character. If you do, you will have built character, depth and confidence.