Because Dbg sells krono for a set price, where you obtained a krono has many variables. One thing for certain is you did not buy a krono from dbg to turn it in for station cash. It won't ever be a "thing."
DBG sells Krono and the only thing you're going to get in return for a Krono from DBG is 30 days of game time. That's all they're worth to DBG and that's all they will ever be worth to DBG