Because they either turn out to be shit and the good ones iron out all their mistakes at arsenal and then when they hit the prime of their career they leave, a long list of senderos, denilson, bendtner, clichy, vela, nasri, fabregas etc and now song, walcott, vpersie proves this.
Why waste time on these unloyal kids, when you can stick with the new policy of buying ready made players 22+ and capable of giving the prime of their career to arsenal.
If we are going to get these youngsters firstly its a waste of transfer time, and secondly it will stop wenger from signing players when he comes up with excuses like his squad is too big (full of youngsters) or signing x will kill y
