If academies focused only on producing players for their club then they would go bankrupt within the year. It is very difficult for a young player to make it at a top club. The reasons to that are many
a- Talent. Very few players has the talent to make it to the top
b- Attitude. A player can be the most talented in the world but if he isn't hardworking then he'll fail
c- Physical development. A player might have both the attitude and the talent but in certain positions, inches matter. Think of a 5ft3 tall CB.He's pretty much useless in the EPL
d- Injuries. You might have the most talented, mature player in the world but injuries can ruin a guy. According to Giggs, Ben was one of the most talented players in the class of 92. Unfortunately a career threatening injury ruined him
e- A manager that believes in giving kids a chance
f- Little competition for places. Its pointless being a 17 year old wonderkid if the competition for places is ridiculously high.
What academies do to remain profitable is buy/raise young talent, develop them and then sell them up. That pays the bills. Take Immobile for example. He was bought by Juventus for 80k when he was just 18 year old, then they loaned him a bit. They sold and re bought parts of his registration rights to Genoa and Torino only to be sold to Dortmund for 17m. That's one hell of a profit. I won't be surprised if we bought Bishop to make a clean profit later on.