WWW - I think it depends on how you define the term backup plan. For example, I see my backup (my grad job) as security so as to be able to keep up repayments on any debts I might entail over the next few years whilst training, and afterwards whilst looking for pilot jobs. I guess others may see it this way too.
This isn’t to say that anyone who really wants their office to be in a cockpit cannot work hard, save hard and train hard after leaving school whilst starting e.g. an apprenticeship or similar! – I have many friends who’ve done this and they earn a nice packet, albeit not as pilots.
The whole topic is very subjective and there is no right or wrong answer - of course if you lose your license after X years you're likely to start from the bottom in another industry and thus the degree is useless, but I'm pretty sure given a slight bit of common sense and experience an ex-pilot could land a decent ground job within aviation.
FlightDeckDave - totally agree on the 50% thing. Some of the most important things I've learned are dependency from the parents and friends, money/time management and interacting with other people.