It’s hardly the only fee, either.
Net profit was $6.7B meaning literally all of their net revenue (a total of 2.25% of gross revenue) was accounted for from these ancillary fees.
But their inflation-adjusted cost went down 36% since 1995.
There were a total of about 1 billion emplanements by US carriers in 2024, ish, so we're talking about a total of about $6 per passenger per year. They really are insignificant.