Many players option for playing time instead of big clubs. Playing in a "farmer league" as an 18-year old could be the better step, because the most important thing for a young player is experience against men. Ajax, Salzburg, etc. are mor interesting for a teenager, than Manchester United, simple as that. Manchester United can offer a great history, but is not focused on youth development. Ajax and Salzburg have great modern academies, etc. (a level above Manchester United ?), they play internationally and the development of young players is part of their philosophy. As a United player it is all about winning...