Is it wrong/unethical/extractive/in bad taste for companies to require applicants to produce valuable work "for free" when applying? Are there exceptions?

E.g. write an investment thesis, do competitor research, put together a pitch deck, prototype a new feature, etc.

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Capstone projects in the final semesters exist for a reason, if the employer want to assess the skill of someone seeking employment those projects are enough to gauge the skill set. 

Anything apart from this should be rewarded, however current job market is so bleak many employers are exploiting individuals who seek employment. Such a sad state of affairs (