LSG,
Well for an 'out of towner' to travel to/from LCY by surface can be a pain in the butt and if SEN prices, both to the operator and the passengers, might be cheaper than LCY, which can't take too much traffic due to the size of the place, then why should LCY maintain any monopoly?
I was referring, by those aircraft types, to such operators as KLM, Lufty, Swiss, Air France, SAS, Austrian etc.
Operators like to develop routes, i.e. they start off a route with smaller aircraft in hope that it will develop to larger aircraft ..... one can't do too much developing in/out of LCY!