YEGaircanada, I think the whole thing even has a bit of an accelerator-effect built into it: imagine someone wanting to travel from his/her "home"-airport to a destination X, which isn't offered from there, but only from the bigger airport "next-door".
Now, the same person wants to fly to a destination Y, which - again - is only offered from the bigger airport...
This person will probably, at most, ask one or two more times of a needed destination is offered from "home", but if it's always just from the "big" airport, the asking for flights from the nearer airport will cease at some point.
This way, passengers are pulled out of the smaller airports, making them (based on pure pax statistics) less interesting for airlines to start offering new services from there, or at some point even reducing their presence at the smaller airport - the result being that, obviously, the airport is even less attractive for passengers, making them chose the larger airport even more frequently...
Only if, at some point, an airline decides to build up a bunch of new services from one of these underutilized airports (JetBlue at LGB
comes to mind) will these airports be interesting again.