Just because a 250hr wonder can pass a A320 check ride, does not mean they deserve to be there. Modern jets are highly automated wonders of technology, but when that technology breaks down (and it does happen), they revert to becoming just airplanes again. And when unexpected things happen quickly you need to be able to stow emotion, think clearly and get the job done.
The point is that the time and effort one puts in before they are in the seat of that shinny jet for the first time does more than build character. It weeds out those who do not have the commitment to treat every aspect of their environment and team with respect. Of course slinging bags and fuelling planes does nothing for your hands and feet skills, but it does put pressure on someone to think quickly, react to the unexpected and work with a team to accomplish a common goal. It's a way for an employer to assess whether or not they should advance said person to subsequent roles with progressively greater levels of responsibility. Basically a good employer knows what we all know. Anyone with enough money can pay for all the flight training in the world, but still not have the qualities to operate a commercial aircraft safely, both in normal an abnormal situations. And there is no easy way to determine these qualities other than to witness them in action.
I spent a few years "paying my dues" in the Canadian north both in and out of the cockpit, but what I realize now is that the experience I gained there has made me a better pilot and hopefully a better person. Now that I do fly a shinny jet and all my training is in simulators, I'm very grateful that my metal has been tested in less than ideal situations (including a few inflight emergencies). Because those experiences both on the ground and in the air have given me the confidence that I will be able to react well in a bad situation, tempered with the humility that me and my team can only do our best.
Good luck to all of us, hopefully we can avoid more 37k plunges.