Those people are probably thinking that that $2/day per card is going to ultimately end up being more if the price of their coins go up.  For example, I started mining ETH with a single r9 290 back in early 2016 and I think I was getting something like 0.5 ETH/day.  At the exchange rate back then, I was generating about $5/day.  However, the price of ETH has skyrocketed since then so that in today's exchange rate, I was effectively generating almost $600/day.  I'm just guessing, but they might be thinking along those lines—gambling on an increased coin price.  I'm not sure why they wouldn't just buy the coins themselves instead though, unless they feel that having a potentially resellable physical GPU is less risky, but at these card prices, that seems like a dubious hedge.