I can't understand the logic of airlines trying to steal market share by doing things like that, going head to head with TCX, why not offer different destinations, more variety for passengers and still offering competition instead of going straight into the exact same routes!?
It's how business works, you go after the market where you feel you can make money and to do that they need to steal market share from the other guy whilst growing the existing market and keeping fares high enough to minimise losses while that happens. In terms of CAN and SFB, they're defending their own market share in London to stop existing Thomson LGW customers popping off to Stansted to use Thomas Cook.