Hmm, I would think the root cause would be there aren't enough good jobs to go around and there haven't been for decades if ever, and so even if we provided boatloads of training and social work and whatever for everyone to "rehabilitate" them and everyone wanted to work etc. etc., there still aren't enough good jobs to go around, end of story!
It doesn't have to be. The remedy requires society as a whole changing what it means for a job to be "good" to something that is sustainable (and indeed that's going to result in changes to all jobs in society), and then fulfilling the obligation of making every job good.
By a "good job" I really only meant paying enough so that you aren't working and falling into the working poor, I meant paying enough so that working manages to lift one out of poverty. It was shorthand, I had nothing grander in mind, and was merely saying that the economic situation of having enough jobs to both employ everyone AND make sure they are lifted out of poverty by work alone without any government aid doesn't exist, so therefore ... government aid becomes a necessary part of any such system.

Of course businesses in their employer role also benefit from high unemployment but that's an aside.
No, it isn't. Rewarding exploitation legitimizes it and works against society changing what it means for a job to be "good" to something that is sustainable
Well by "an aside" I mean this high unemployment situation seems to be of benefit to employers so one might get conspiratorial (and I don't consider the term conspiratorial insulting) and say that no wonder we get dozens of bills on everything under the sun many that are wildly unpopular and yet what is the one bill that never passes: a jobs bill or any bill that addresses the unemployment situation! Even though it might be extremely popular! So you might start to wonder about things like intent and so on and if *they* (powers that be) want this high unemployment situation. But conspiracy, and all getting together in a room over cigars to plan the situation, is not necessary, even in good times you have the so called "natural unemployment rate", which is that unemployment that is considered naturally part of the economy, so if we're going to live in a system that naturally always has some unemployment then ... government aid naturally exists alongside it to plug that gap.