That's not entirely true. If you keep up with the Russian community, the owners of the site (or at least the two guys who launched the site) are very likely known to some people. The amount of money lost is also nothing to sneeze at for many creditors, some of whom are likely capable of locating said owners and, well, killing them if necessary. They already have a target on their back from the US government; that's not a massive issue if they stay in countries with no extradition treaties with the US and stop processing fiat (at least through the USD and EUR banking systems; maybe some limited cash and Ruble options are possible).

The largest motivating factor for them to issue at least partial refunds is to prevent having another target on their back from nefarious creditors who have the means to find them.