Doing so can actually cost you money.
Reason 1: If you exempt debit card holders from paying your card processing fee, you will avoid that customers eventually interrupt their ticket purchase process just in the crucial moment when handing over the money. He or she may feel deceived by this unexpected late charge or may want to explore options to avoid the fee. In any case, you must give customers easy-to-use and widely accepted payment options.
Reason 2: This will make your own insurance offering more attractive as customers will tend less to use their credit card with its included automatic travel insurance.
This generates new ancillary revenue opportunities and won’t turn off customers during the payment process!