Ah, but the willing aren't able and the able aren't willing. In any case, I'd avoid companies that recklessly fleece applicants just because they can. Once you've proven your worth professionally, begging for scraps is pathetic in any job market. For every greedy business with ten desperate applicants, there's an honest organization or untapped market ready to pay fairly for what value you offer.

The question I consider when asked to perform for free: why should anyone simply donate their knowledge to a profitable business after spending a lifetime to attain it?

Doing something because you can is the worst reason to do so.