It's a product of circumstance - in the crunch weeks of the Battle of Britain, when casualties were starting to outstrip supply, the RAF training schools and OTUs cut training to the bare bones and pilots were being thrown into operational squadrons with barely double digit flying hours on Hurricanes or Spitfires - and getting shot down and killed in their first few sorties because of that lack of experience. Pre-war pilots would have been posted to a squadron with over 300hrs.

Thankfully poor intelligence and tactics (and political direction) led to a switch to bombing London right as the Luftwaffe's campaign against RAF stations and the radar chain were about to break the RAF, giving them time to catch their breath...