Brian,
You are hitting on those crucial 20% of pax who no doubt make up 80% of FR's profits, MOL is well versed in the rule of Pareto.
Ryanair are so easy to hate as an airline, but when it comes to running a business, their margins are leaps and bounds ahead of everyone else. Sure, they have learned from Southwest etc, but having their routes development director ask them some questions about this very topic (ie why Southwest don't ramp up their fares in the last week before departure) at the World Low Cost Airlines Congress was very telling.
Who's profit margins are twice those of Southwest?
By all means shop around, but as you say too many people don't bother, only then to pick up a Hertz rental car booked through FR, and spend ages queing for it, boosting FR's bottom line further.