Aside from actual first sale doctrine and the like, morally, I am curious what doesn't seem fair about not discriminating against how the purchaser uses what th

Aside from actual first sale doctrine and the like, morally, I am curious what doesn't seem fair about not discriminating against how the purchaser uses what they bought? What doesn't seem fair is you getting to say what your product was meant for and keeping others with other potential uses from purchasing/using.