I have written to Kayak suggesting this in the past. Without such a feature, the hidden charges and nickle-and-diming will just get worse. The best explanation

I have written to Kayak suggesting this in the past. Without such a feature, the hidden charges and nickle-and-diming will just get worse. The best explanation I heard (from elsewhere) was that if Kayak automatically included any fees, then some users might see a lower price on another site and mistakenly conclude the Kayak didn't actually have the lowest prices. But this seems obviously solvable by making it a non-default option and displaying the price as "$X ($Y fare + $Z fees)".