I'm sure it has been discussed before, but what factors push people away from say two-day internships? Is it because these things are so short that they too can

I'm sure it has been discussed before, but what factors push people away from say two-day internships? Is it because these things are so short that they too can eventually be gamed? Or is it because you need to have staff of the same specialty dedicating their resources to a potentially short-lived investment?