When recent graduates accept this type of employment, the opportunity is called internship.
When adults --"experienced hires"-- accept this type of employment, the opportunity is called spec and one of the oldest bait-and-switch manuevers in every business.
In either case, the hiring authority who solicits free labor is an asshole, regardless of any quantitative analysis of cyclical stressors one employs to exculpate exploitation of people desperate to earn a wage.
re: "...anyone can make media now. Which is true, but hardly anyone can make media and get paid for it - unless they create a feudal-enclosure and try to monetise it."
Automation "democratizes" "media" quantity and quality by eliminating (or rationalizing) the vagary of "value added" by labor in production processes. The "feudal-enclosure" to which you may have alluded is supply of and demand for package software operators by corporate publishers, advertisers included. And advertisers' limits on "media placement" expenses --online and offline broadcast or print-- is really what drives agency growth (employment and billings), as you, I'm sure discovered in your exposé of hiring practices at boutiques and conglomerates.
Pervasive "creativity" is not a perequisite of revenue generation.
ISVs "monetize" demand for package software competences --e.g. auto-focus, "plug-in" interoperability, keyboard short-cuts, typing speed, derivatives volume-- by continuous sales of operating licenses to continuously obsolescent package software. Diversity is the key to economic and political evolution.
And some of them had spent time on what might considered pro bono work offering feedback on portfolios - which was clearly a self-interested way to recruit, but seemed more effort than the usual interview round.
The justification for placements was that it gave the 'employee' a chance to learn the jargon and rhythms of the workplace. Whereas those arrived fresh from college needed to have everything spelled out for them.
I'm not sure how long it would take to put together jargon buster, or how much paper it would need. Not long, and not much, at a guess.
Being able to massage client egos - and, occasionally, other body parts - seems to be a more useful talent.
The relationship is Renaissance client-patron, with the patron showering boutiques with largesse in return for praise and confirmation of the patron's significance - and hopefully a few sales.
Studios don't understand their own power in this relationship. They seem to assume that corporate benediction is the ultimate reward.
But if the entire ad industry downed pencils tomorrow, clients would be truly fucked.
If so, describe for our audience the meaning of "gang bang." Diversity is the key to economic and political evolution.