I mean you can, it's just not the taxes most people would think it is and it forfeits the remainder of the ticket value. The IRS (and most other taxing entities) position for the majority of taxes is that they are imposed based on airfare being purchased, not necessarily utilized, so they aren't refundable if the fare isn't refundable. There is a small subset of taxes that are for services rendered by government agencies related to the passengers travel or enplanement taxes which are only remitted if the flight coupon is actually used. In the US it is things like the 9/11 security fee, APHIS, and customs user/immigration service fees, so you're looking at like ~$15 in taxes you could get refunded; but of course getting those refunded then means you're forfeiting the rest of that ticket; so rarely if ever a case to do it.