Transparently, I ask that question because I’m wary of creating a system where employers have a direct economic incentive to not hire people who would be likely to receive government benefits. Nearly the last thing someone on government support needs is employers not wanting to hire them.
If that means (as I think it does) that corporations are not individually tagged for their specific workers’ benefits, so be it.
I’m also opposed (though less strongly) to creating a taxation system where taxation levels are not reasonably predictable, given enough effort. If I don’t know whether Joe is going to cost me $30K/yr or $50K/yr and I’ve got 500K “Joes”, that’s $10 billion dollars of annual uncertainty. Even if you cap the uncertainty to between 25% and 75% of the range, it’s $5B. For $5B/yr, I can find a bunch of other arrangements that give me less exposure (most obviously using subcontractors who aren’t themselves “large companies”, but even if they are, it becomes “their problem” which is better than “my problem”).
As much as I support local, family-owned businesses on an individual level, I also recognize that for the vast majority of people, cheaper goods are much better for their lives.
I do wish we forced large corporations to pay for any government benefits that their workers collect, though, and continue to push for living wages that make sense at the local level.