Fees and taxes, yes. They are very low priority and you need to be careful who to use them with, and where.
Pre-COVID there used to be a joke that D3's (these buddy passes) are for people you don't like. If used cautiously, they can be useful at times. The fees are expensive though, 60-80 per domestic leg and 100-150 intl.
The sweet spot is long haul stuff where you can find a flight with seats in business class. But if someone wants to go to Cabo for Spring Break, that is not going to happen.