Flying done properly is safer than crossing the street and I'm happy to take that risk. Flying through an ash cloud is not something that generally turns out good for aircraft engines; even if an initial inspection shows that all appears fine with the aircraft and first stage fan blades, a borescope inspection may reveal clogged turbine cooling air passages (see Grindle, T., J., and Burcham, Jr., F. W., 2002, Even Minor Volcanic Ash Encounters Can Cause Major Damage to Aircraft).
If once all this is done airlines feel the need to charge more for tickets then so be it - I'm happy to pay more if it's because of safety concerns.
They're scared of ceasing to exist, i.e. bankruptcy.