That's definitely true, but going to grad school or the military as a "backup" is probably a bad idea. There are worse holding patterns, but there are also a lot better ones.
In general, if you don't know what you want to do, making a multi-year commitment is a bad idea.
Follow through is what makes it a good or bad choice. A 20 year military stint can be extremely profitable. Join at 18, get a free collage, and Masters degree (or two), then leave and become a consultant at 200+k/year. Add in all those sweet long term benefits such as a pension and it's not a stupid choice if you know how to network and try and get promoted. Then again you can also be a grunt get shot and die but the military is not as risky as most people assume.
Anyway, I don't think the problem is the multi-year commitment it's people that fail to maximize the value of that choice. I think the people who don't really know what they want are going and get a Masters / PHD in history because it's more fun than working a real job are the type of people who will fail at most things.
In general, if you don't know what you want to do, making a multi-year commitment is a bad idea.