Others have argued the point at depth, but its somewhat more simple than that.

Is it plausible that Kagi's financials require them to run a tighter ship than established players?

Conversely, is it plausible that they are so popular that they can afford to be deaf to the negative UX of the extra sub?

I would suggest that the answers to those, and a quick survey of the heavy costs agentic use has imposed on site operator over the past few year5, suggest that this is a reasonable compromise that keeps costs down for the average user and moves agentic users to the API-fee paradigm that is already rather common.