By describing it as a queue-busting time-saving convenience fee compared to making flight-only pax who do not have hold baggage and have paid no other ancillary fees wait 30+ mins to be given a piece of paper.
More than 1 airport has a fast-track queue at security search in exchange for paying a fee, either directly or by spending more on a plane ticket - the security searching is just the same but the airport offers to save a passenger's time in exchange for the passenger paying more (and the airport not having to increase staffing levels)
I agree this is a lousy customer service proposition, but I'm wondering whether an airline would want to try this on just to boost profits. It's been tried in the past and I wonder if an airline would try it again in the future