Yes, Aerospace Engineers don't live in London because there are very little (if any) aerospace jobs in London. Biggest aerospace employers in the UK are BAE Systems and Airbus, and both have factories in much cheaper locations (Wales, Northwest of England).

You're basically comparing "super specialised job in the middle of nowhere with very low cost of living" vs a "super specialised but much more needed job in multiple high cost of living locations" (Seattle metro area, LA metro area to name a few).