While I agree it is not a good thing to stare at the primary, I do believe that almost all college QB's do it at least 80% of the time unless they end up throwing to the secondary receiver. The QB has to really be confident in his and the receiver's knowledge, ability to read the D and timing and that comes with many successful practices against a defense I think. Also, I think the main reason a QB needs to look off a receiver is to prevent a safety or nickle back from getting a good read, mostly the safety. The corner is usually focused on his man, a peak at the QB can mean disaster for him.